There are four people who want to cross a rickety bridge; they all begin on the same side. You have 17 minutes to get them all across to the other side. It is night, and they have one flashlight. A maximum of two people can cross the bridge at one time. Any party that crosses, either one or two people, must have the flashlight with them. The flashlight must be walked back and forth; it cannot be thrown, for example. Person 1 takes 1 minute to cross the bridge, person 2 takes 2 minutes, person 3 takes 5 minutes, and person 4 takes 10 minutes. A pair must walk together at the rate of the slower person’s pace.

Required:
What is the shortest time needed for all four of them to cross the bridge?

Answers

Answer 1

Answer:

The shortest time needed for all four of them to cross the bridge = 17 minutes

Explanation:

As given ,  to cross the bridge

Person 1 takes 1 minute,

Person 2 takes 2 minutes,

Person 3 takes 5 minutes, and

Person 4 takes 10 minutes.

For the first time ,

Person 1 and Person 2 will go to cross the bridge

As Person 2 takes 2 minutes

So, total time taken by Person 1 and person 2 together will be 2 minutes

Now,

Person 1 will come back with flashlight.

He takes 1 minutes.

So, Total time becomes 2 + 1 = 3 minutes

Then,

Person 3 and Person 4 will cross the bridge

As Person 4 takes 10 minutes

So, total time taken by Person 3 and person 4 together will be 10 minutes

So, Total time becomes 3 + 10 = 13 minutes

Now,

Person 2 will come back with flashlight.

He takes 2 minutes.

So, Total time becomes 13 + 2 = 15 minutes

Then,

Person 1 and Person 2 will cross the bridge

As Person 2 takes 2 minutes

So, total time taken by Person 1 and person 2 together will be 2 minutes

So, Total time becomes 15 + 2 = 17 minutes

∴ we get

The shortest time needed for all four of them to cross the bridge = 17 minutes


Related Questions

Engineer drawing:
How can i draw this? Any simple way?

Answers

Make 4 triangles left right up down and they must be connected with no gaps then make more triangles into the triangle about three times for each of them then add rectangles or lines to the drawing

Perform the following unit conversions. Please do not use an on-line unit converter since this problem is given to you as practice in preparation for what you need to be proficient in:

a. 180 in^3 to L
b. 750 ft-lbf to kJ
c. 75.0 hp to kW
d. 2500.0 lb/h to kg/s
e. 120 psia to kPa
f. 120 psig to kPa
g. 300 ft/min to m/s
h. 125 km/h to miles/h
i. 6000 N to Ibf
j. 6000 N to ton

Answers

Answer:

The answers are below

Explanation:

a. 180 in^3 to L

1 in³ = 0.0164L

180 in³ = [tex]180\ in^3*\frac{0.0164\ L}{1\ in^3}= 2.95\ L[/tex]

b. 750 ft-lbf to kJ

1 ft-lbf = 0.00136 kJ

750 ft-lbf  = [tex]750\ ft-lbf *\frac{0.00136\ kJ}{1\ ft-lbf} =1.02\ kJ[/tex]

c. 75.0 hp to kW

1 hp = 0.746 kW

75 hp = [tex]75\ hp*\frac{0.746\ kW}{1\ hp}=55.95\ kW[/tex]

d. 2500.0 lb/h to kg/s

1 lb/h = 0.000126 kg/s

2500.0 lb/h = [tex]2500.0\ lb/h*\frac{0.000126\ kg/s}{1\ lb/h} =0.315\ kg/s[/tex]

e. 120 psia to kPa

1 psia = 6.89 kPa

120 psia = [tex]120\ psia*\frac{6.89\ kPa}{1\ psia} =826.8\ kPa[/tex]

f. 120 psig to kPa

1 psig = 6.89 kPa

120 psig = [tex]120\ psia*\frac{6.89\ kPa}{1\ psig} =826.8\ kPa[/tex]

g. 300 ft/min to m/s

1 ft/min = 0.005 m/s

300 ft/min = [tex]300\ ft/min*\frac{0.005\ m/s}{1\ ft/min} = 1.5\ m/s\\[/tex]

h. 125 km/h to miles/h

1 km/h = 0.62 mph

125 km/h = [tex]125\ km/h*\frac{0.62\ mph}{1\ km/h} =77.5\ mph[/tex]

i) 6000 N to Ibf

1 N = 0.2248 lbf

6000 N = [tex]6000\ N*\frac{ 0.2248\ lbf}{1\ N}=1348.8\ N[/tex]

j. 6000 N to ton

1 N =  0.000102 Ton-force

6000 N = [tex]6000\ N*\frac{ 0.000102\ Ton-force}{1\ N}=0.612\ N[/tex]

Consider a Rankine cycle with reheat using water (steam) as the working fluid. Saturated liquid at 100C exits the condenser. The fluid exits the boiler at 6500C, 20000 kPa. The cycle uses a single reheater with operating pressure 200 kPa and exit temperature 5000C. The mass flow rate of water (steam) in the cycle is 40 kg/s. The operation of the turbines and pump are adiabatic and have isentropic efficiency 0.90. As usual, neglect pressure losses in piping, boiler, reheater, and condenser. Compute: quality at the exit of the high-pressure turbine.

Answers

PLEASE HELP I need help too !!


PWM input and output signals are often converted to analog voltage signals using low-pass filters. Design and simulate the following: a PWM signal source with 1 kHz base frequency and adjustable pulse-width modulation(PWM source), an analog filter with time constant of 0.01 s. Simulate the input and output of the low pass filter for a PWM duty cycle of 25, 50, and 100%

Answers

Answer:

Attached below

Explanation:

PWM signal source has 1 KHz base frequency

Analog filter : with time constant = 0.01 s

low pass transfer function = [tex]\frac{1}{0.01s + 1 }[/tex]

PWM duty cycle is a constant block

Attached below is the design and simulation into Simulink at 25% , 50% and 100% respectively

A freezer compartment consists of a cubical cavity that is 2 m on a side. Assume the bottom to be perfectly Problems 49 CH001.qxd 2/24/11 12:03 PM Page 49 insulated. What is the minimum thickness of styrofoam insulation (k 0.030 W/m K) that must be applied to the top and side walls to ensure a heat load of less than 500 W, when the inner and outer surfaces are 10 and 35 C

Answers

Answer:

30 mm is the minimum thickness that must be applied.

Explanation:

Given the data in the question;

Using Fourier's equation. the heat rate is  

q = kA(ΔT/Δx)

where

A is the surface area, we must consider all surfaces through which the heat can dissipate through

i.e 2×2 for one wall gives you 4m²,

there are 5 walls, so we will  have 20m² for surface area.

k is thermal conductivity of the styrofoam ( 0.030 W/m K)    

q is the heat loss (500 W  )

ΔT is the Temperature difference ( 35 - 10) = 25°C

Δx  = ?

So we substitute

500 = (0.030)(20)(25/Δx)

500 = 0.6 (25/Δx)

500 = 15 / Δx

Δx = 15 / 500

Δx = 0.03 m = 30 mm

Therefore, 30 mm is the minimum thickness that must be applied.

A site is underlain by two layers of normally consolidated clayey sand. The unit weights of the top layer are 19 and 21 kN/m2 and the layer is 6 meters thick. The unit weights of the bottom layer are 20 and 22 kN/m, and the layer is 8 meters thick. Below the bottom layer lies bedrock. The water table is located 2 meters below the ground surface. The top layer soil has a friction angle of 38 degrees, a cohesion intercept of 20 kPa, and an undrained strength of 160 kPa. The bottom layer soil has a friction angle of 33 degrees, a cohesion intercept of 10 kPa, and an undrained strength of 120 kPa. Point A is located 9 meters underground. All layers have a lateral stress ratio of 0.5.

Required:
a. Draw the profile neatly, add dimensions, and draw a tree on the ground surface.
b. Determine the geostatic vertical effective stress and the geostatic horizontal effective stress at point A.
c. Draw the Mohr Circle to determine the effective stress that acts at point A on a plane inclined 10 degrees counter-clockwise from the horizontal plane. Make sure the Mohr Circle is a well-drawn circle

Answers

Answer:

A) attached below

B) Geostatic vertical effective stress ( бv )

= 119.33 KN/m^2

Geostatic horizontal effective stress ( бn )

= 59.66 KN/m^2

C) attached below

Explanation:

attached below is a detailed solution

A) attached below

B) Determine the geostatic vertical effective stress and the geostatic horizontal effective stress at point A

Geostatic vertical effective stress ( бv )

= 119.33 KN/m^2

Geostatic horizontal effective stress ( бn )

= 59.66 KN/m^2

C) attached below


Drum brakes are usually designed so that the condition of the lining can be checked even if the drum has not been
removed.

Answers

Answer:

no it has to be removed

Explanation:

It is completely inappropriate to mention that the drum brakes are usually designed so that the condition of the lining can be checked even if the drum has not been removed. Therefore, the statement given above is false.

What is the significance of drum brakes?

Drum brakes can be referred to or considered as the types of brakes that are useful in application of brakes to an object, such as wheels, in motion. To understand better, it can be stated that the system of braking under drum brakes is completely in contrast to that of disc brakes.

Drum brakes have a hydraulic pressure, which means that if the condition of lining is to be checked, removal of drums becomes essential. If the drums are not removed, correction or alignment of wheels cannot be performed.

Therefore, the significance regarding drum brakes has been aforementioned, and the statement given above with respect to their removal also holds false.

Learn more about drum brakes here:

https://brainly.com/question/14937026

#SPJ2

2.) Technician A says that milky colored ATF could indicate a leaking transmission cooler in the radiator.
Technician B says that milky colored ATF could indicate the presence of leak detection dye.
Who is right?
OA. A only
OB. B only
OC. Both A and B
OD. Neither A nor B

Answers

I think a is the correct answer

A river has an average rate of water flow of 59.6 M3/s. This river has three tributaries, tributary A, B and C, which account for 36%, 47% and 17% of water flow respectively. How much water is discharged in 30 minutes from tributary B?

Answers

Answer:

50421.6 m³

Explanation:

The river has an average rate of water flow of 59.6 m³/s.

Tributary B accounts for 47% of the rate of water flow. Therefore the rate of water flow through tributary B is:

Flow rate of water through tributary B = 47% of 59.6 m³/s = 0.47 * 59.6 m³/s = 28.012 m³/s

The volume of water that has been discharged through tributary B = Flow rate of water through tributary B * time taken

time = 30 minutes = 30 minutes * 60 seconds / minute = 1800 seconds

The volume of water that has been discharged through tributary B in 30 seconds = 28.012 m³/s * 1800 seconds = 50421.6 m³

Please calculate the energy stored in a flying wheel. The steel flying wheel is 10 metric tons, in adiameter of 10m, and it rotates at a speed of 1000 rpm. The steel density is 8050 kg/m^3. When energyis fully released, the flying wheel stops its rotation.

Answers

Answer:

685.38 MJ

Explanation:

Given that:

mass = 10 tons = 1.0 × 10 ⁴ kg

diameter D = 10 m

radius R = 5 m

speed N = 1000 rpm

Using the formula for K.E = [tex]\dfrac{1}{2}I \omega^2[/tex] to calculate the energy stored

where;

[tex]= \dfrac{2 \pi \times N}{60}[/tex]

[tex]= \dfrac{2 \pi \times 1000}{60}[/tex]

= 104.719 rad/s

Hence, the energy stored is;

[tex]= \dfrac{1}{2}\times (\dfrac{MR^2}{2}) \times \omega^2[/tex]

[tex]= \dfrac{1}{2}\times (\dfrac{10^4\times 5^2}{2}) \times 104.719^2[/tex]

= 685379310.1

= 685.38 MJ

Determine the voltage drop from the top terminal to the bottom terminal, vab, in the right hand branch and, vcd, in the left hand branch of the circuit. Determine each voltage drop based on the elements in the corresponding branch.

Answers

Answer:

Hello your question is incomplete attached below is the missing part of the question

answer ;

voltage drop in the Vcd branch = 30 V

Voltage drop in the middle branch = 40v - 30v = 10 volts

voltage drop in AB = 60 + ( -600 * 0.05 ) = 60 - 30 = 30 volts

Explanation:

Determine voltage drop from top terminal to bottom terminal ( Vab ) in the right hand branch and Vcd in left hand branch

40v and 50mA are in series hence;  Ix = 50mA

also Vcd = 30V

CD is parallel to AB hence; Vcd = Vab = 30 V

Vab = ∝*Ix + 60 v

 30v  = ∝ ( 50mA ) + 60

therefore ∝ = -600

voltage drop in the Vcd branch = 30 V

Voltage drop in the middle branch = 40v - 30v = 10 volts

voltage drop in AB = 60 + ( -600 * 0.05 ) = 60 - 30 = 30 volts

3.) Technician A says that a scan tool can be used to verify engine operating temperature,
Technician B says that a refractometer can be used to verify engine operating temperature.
Who is right?
OA. A only
OB. B only
OC. Both A and B
OD. Neither A nor B

Answers

I think it is Both A and B

A brass alloy rod having a cross sectional area of 100 mm2 and a modulus of 110 GPa is subjected to a tensile load. Plastic deformation was observed to begin at a load of 39872 N. a. Determine the maximum stress that can be applied without plastic deformation. b. If the maximum length to which a specimen may be stretched without causing plastic deformation is 67.21 mm, what is the original specimen length

Answers

Answer:

a) the maximum stress that can be applied without plastic deformation is 398.72 N/mm²  

b) length of the specimen is 66.97 mm

Explanation:

Given the data in the question;

a) Determine the maximum stress that can be applied without plastic deformation

when know that; maximum stress σ[tex]_{max}[/tex]  = F / A

where F is the force in the rod ( 39872 N )

A is the cross-sectional area of the rod ( 100 mm² )

so we substitute;

σ[tex]_{max}[/tex]  = 39872 N / 100 mm²

σ[tex]_{max}[/tex]  = 398.72 N/mm²

Therefore, the maximum stress that can be applied without plastic deformation is 398.72 N/mm²  

b)  

strain in the members can be calculated using the expression

ε = σ / E

where σ is the stress in the rod

E is the module of elasticity (  110 GPa = 110000 N/mm² )

(Sl-L) / L = σ/E

where Sl-L is the change in length of the member

L is the original length of the specimen

so we substitute

(67.21 - L) / L = 398.72 / 110000

110000( 67.21 - L) = 398.72L

7393100 - 110000L = 398.72L

7393100 = 398.72L+ 110000L

7393100 = 110398.72L

L = 7393100 / 110398.72

L = 66.97 mm

Therefore; length of the specimen is 66.97 mm

 

why you so mean to me? leave my questions please. answer them

Answers

Answer: Why is even here then.

Explanation:

A Russian rocket engine (RD-110 with LOX-kerosene) consists of four thrust chambers supplied by a single turbopump. The exhaust from the turbine of the turbopump then is ducted to four vernier nozzles (which can be rotated to provide some control of the flight path). Using the information below, determine the thrust and mass flow rate of the four vernier gas nozzles. For individual thrust chambers (vacuum): F= 73.14 kN, c = 3279 m/sec Overall engine with verniers (vacuum): F= 297.93 kN, c = 3197 m/sec.

Answers

Answer:

- Vernier thrust is 5.37 kN

- mass flow rate of the four Vernier gas nozzles is 0.4048 kg/s

Explanation:  

Given that;

For individual thrust chambers (vacuum);

Fc = 73.14 kN ,  Cc = 3279 m/sec

For Overall engine with Vernier (vacuum);

Foa = 297.93 kN = ,  Coa = 3197 m/sec.

- determine the Vernier thrust

Vernier thrust Fv =  Foa - ( 4 × Fc )

Vernier thrust Fv  = 297.93 - ( 4 × 73.14)

Vernier thrust Fv  = 297.93 - 292.56

Vernier thrust Fv  = 5.37 kN

Therefore, Vernier thrust is 5.37 kN

-

Vernier mass flow rate;

we know that

[tex]Co_{a}[/tex] = Fc + Fv  / mc + mv

mv = Foa/Coa - Fc/Cc

we convert kilonewton to kilograms

1 kn = 102 kg

Fc = 73.14 kN = 73.14 × 102 = 7460.28 kg

Foa = 297.93 kN = 297.93 × 102 = 30388.86 kg

we substitute

mv = (30388.86 / 3197) - (( 4 × 7460.28) / 3279)

mv = 9.5054 - 9.1006

mv = 0.4048 kg/s

Therefore, mass flow rate of the four Vernier gas nozzles is 0.4048 kg/s

Axial forces in a column due to service loads are as follows (assume the live load used in these calculationsis less than 100 psf):Dead:150 kcompressionLive:280 kcompressionRoof Live:40 kcompressionSnow:50 kcompressionWind:120 kcompression or tensionEarthquake:200 kcompression or tension1. Compute the required axial strength,TuandPu, for this column in tension and compression usingLRFD load combinations. (Neglect self-weight.)2. Describe the loading scenario that represents the worst case tension and compression loading for thecolumn (remember, wind and earthquake loading can act in either direction).

Answers

Answer:

a) attached below

b) The worst case in tension is case ( 9-7 ) b which is

  = -65k

  The worst case in compression is case ( 9-5 ) a which is

 = 670 k  

Explanation:

Given data :

D = 150k , L = 280k , Lr = 40k , s = 50k , w = ± 120k

E = ± 200k

attached below is a detailed solution to the given problem ( problem 1 )

A)  attached below

b) The worst case in tension is case ( 9-7 ) b which is

  = -65k

  The worst case in compression is case ( 9-5 ) a which is

 = 670 k  

64A geothermal pump is used to pump brine whose density is 1050 kg/m3at a rate of 0.3 m3/s from a depth of 200 m. For a pump efficiency of 74 percent, determine the required power input to the pump. Disregard frictional losses in the pipes, and assume the geothermal water at 200m depth to be exposed to the atmosphere.

Answers

Answer:

835,175.68W

Explanation:

Calculation to determine the required power input to the pump

First step is to calculate the power needed

Using this formula

P=V*p*g*h

Where,

P represent power

V represent Volume flow rate =0.3 m³/s

p represent brine density=1050 kg/m³

g represent gravity=9.81m/s²

h represent height=200m

Let plug in the formula

P=0.3 m³/s *1050 kg/m³*9.81m/s² *200m

P=618,030 W

Now let calculate the required power input to the pump

Using this formula

Required power input=P/μ

Where,

P represent power=618,030 W

μ represent pump efficiency=74%

Let plug in the formula

Required power input=618,030W/0.74

Required power input=835,175.68W

Therefore the required power input to the pump will be 835,175.68W

Other Questions
Chris paid $3,069 for 3 iphones. Each iphone costs the same amount. How much did each iphone cost? Solve this problem using a strategy of your choice. On October 1, 2018, Jay Pryor established an interior decorating business, Pioneer Designs. During the month, Jay completed the following transactions related to the business:Oct. 1 Jay transferred cash from a personal bank account to an account to be used for the business in exchange for common stock, $32,800.4 Paid rent for period of October 4 to end of month, $3,180.10 Purchased a used truck for $27,000, paying $3,000 cash and giving a note payable for the remainder.13 Purchased equipment on account, $12,790.14 Purchased supplies for cash, $2,200.15 Paid annual premiums on property and casualty insurance, $4,920.15 Received cash for job completed, $13,780.Enter the following transactions on Page 2 of the two-column journal:21 Paid creditor a portion of the amount owed for equipment purchased on October 13, $4,560.24 Recorded jobs completed on account and sent invoices to customers, $15,680.26 Received an invoice for truck expenses, to be paid in November, $1,440.27 Paid utilities expense, $1,640.27 Paid miscellaneous expenses, $590.29 Received cash from customers on account, $6,560.30 Paid wages of employees, $4,360.31 Paid dividends, $3,640.Required:1. Journalize and insert the posting references for each transaction in a two-column journal beginning on Page 1, referring to the following chart of accounts in selecting the accounts to be debited and credited. For a compound transaction, if an amount box does not require an entry, leave it blank.11 Cash 31 Common Stock12 Accounts Receivable 33 Dividends13 Supplies 41 Fees Earned14 Prepaid Insurance 51 Wages Expense16 Equipment 53 Rent Expense18 Truck 54 Utilities Expense21 Notes Payable 55 Truck Expense22 Accounts Payable 59 Miscellaneous Expense For the following graphed line, what are the slope and y-intercept PLSSSS HELP ASAP! May give brainlest Native American slavery existed in New Mexico because ________________ Each bag of skin contains 2.6 ft. of sand, how many bags of sand will need to be purchased to completely fill the sandbox? Adams car traveled 465.3 miles on 16.5 gallons of gas. Which equation can be used to determine the average number of miles that the car traveled on each gallon of gas?16.5x = 465.3StartFraction x over 16.5 EndFraction = 465.3465.3 x = 16.5StartFraction x over 265.3 EndFraction = 16.5 ASAP I NEED HELP I GIVE COINS!!Based on the picture above, what habitat is this bird best adapted for?ForestOceanMarshDesert Which inequality is equivalent to 4x-2y8?A. y-2x-4B. y2x-4C. y2x-4D. y-2x-4 What benefits did the GI Bill provide? Check all that apply.It provided money to train for a new profession.It guaranteed job placement after school graduation.It promised the ability to attend a college or university.It gave the right to an education for all who served.It offered the opportunity to attend a technical school. This is 10 questions please answer. 1.Write the ratio as a fraction in the simplest form 15 girls to 6 boys. 2.Write The ratio as a fraction in simplest form 24 players: 3 teams.3. Write The ratio as a fraction in simplest fraction form 48 worksheets: 12 students.4. Tell whether the ratios form a proportion 4/7 the 4 is on top of the 7 24/35 the 24 is on top of the 35. 5. Tell whether the ratios form a proportion 11/12 11 top of the 12 33/36 33 on top of the 36. 6. 8/24 8 on top of 24 5/15 5 on top of the 15. 7.3/7 3 is on top of the 7 12/21 12 top of the 21 8. Tell whether the two rates form a proportion 25 cars in 5 days; 60 cars in 12 days.9.14 books in 2 boxes; 20 books in 3 boxes.10.On a monday you swim 12 laps in 30 minutes. On tuesday you swim 15 laps in 45 minutes are these rates porportional? Explain. difference between input work and output work with table The mass of 60 paper clips is 18.0 grams. What is the mass of one paper clip? Estoy tan jodidamente aburrida To determine the concentration of citric acid, you will need to titrate this solution with 0.100 M NaOH. You are given a 1.00 M NaOH stock solution and will need to make enough 0.100 M NaOH to perform 3 titrations. For each titration, you will use 20.0 mL of 0.100 M NaOH solution. Calculate the total volume (in mL) of the diluted solution you will need to prepare for the 3 titrations. Determine the minimum volume (in mL) of 1.00 M NaOH stock solution needed to prepare the 0.100 M NaOH solution. What was the relationship between Greek religion and Greek mythology? The Navys tactic of using _________________ helped win the Mexican-American War and the Civil War.A. TorpedoesB. BlockadesC. RadarD. Smuggling Which of the folllowing is true about the efficiency of the energy conversions in terms of the overall energy available to human shown in these diagrams The probability of an event is 0.001.Which of the following best describes the event?A The event will never occur.B There is a small chance that the event will occur.C The event is likely to occur.D The event will definitely occur. The area of triangle ABC is 4 root 2. Work out the value of x