One pipe can fill a tank in 4 hours. A second pipe can fill the same tank in 5. How long will it take?

Question

One pipe can fill a tank in 4 hours. A second pipe can fill the same tank in 5 hours. How long will it take for both pipes going at the same time to fill the tank? hours______ minutes______ seconds_________

Answer 1

time together / time alone1 + time together / time alone2 = 1 job

t/4 + t/5 = 1

5t + 4t = 20
t = 20/9 hours = 2 and 2/9 hours

2/9 hours = 2/9 * 60 minutes = 13 1/3 minutes = 13 minutes 20 seconds

so 2 hours, 13 minutes, 20 seconds

Answer 2

Solve for how much each pipe will fill the tank in 1 hour:
Pipe 1: 4 hrs / 1 tank = 1 hr / x tank
Pipe 1: 1/4 tank in 1 hour
Pipe 2: 5 hrs / 1 tank = 1 hr / x tank
Pipe 2: 1/5 tank in 1 hour
Therefore in 1 hours' time the tank filled is the total of the two pipes abiltiy to fill in 1 hour:
Pipe 1 + Pipe 2 = 1/4 + 1/5 = 9/20 tank filled in 1 hour
This is a ratio problem of tank/time:
(9/20 tank) / 1 hour = (1 tank) / x hours
Where x = 20/9 hours
Simplified to Hours: x = 20/9 = 2.222...hrs
Simplified to Minutes: 0.22hrs: (0.22hrs)(60min)=13.2min
Simplified to Seconds: 0.2min: (0.2min)(60sec)=12sec
Therefore to fill 1 tank using Pipe 1 and Pipe 2 :
Answer: 2hrs 13min 12sec

Answer 3

COnsider what happens in 1 hour
First pipe fills 1/4 tank, second pipe fills 1/5 so in 1 hour 1/4 + 1/5 = 9/20th of the tank is filled. Therefore itt akes 20/9 hours to fill the tank = 2 2/9 hours.

Alternatively consider 20 hours.
First Pipe fills 5 tanks: second pipe fills 4 tanks - so 9 tanks are filled in 20 hours etc

Answer 4

First pipe takes 4 hours, second pipe takes 5 hours, two together average 4 1/2 hours. Since both going at same time divide 4 1/2 by 2= 2 3/4 hours.

Answer 5

This is a "production problem". The basic equation is:
Tanks filled = SUM(Tanks filled/hour x hours )
Let x be the time to fill 1 tank
1= (1/4) x + (1/5) x
Then 1/.45 = x in hours.
You can figure out the small stuff.

Answer 6

4 * 5 / 4 + 5 = 20 / 9 or 2 2/9 hours. Well 2/9 hours = 120/9 minutes, or 13 1/3 minutes. And 1/3 miute = 60/3 seconds or 20 seconds. The answer is 2 hours, 13 minutes, and 20 seconds.

Answer 7

V = Volume of tank to be filled. Flow Rate1 =V/18 Flow rate 2 = V/24 Final flow rate = V/t, where t = time in hours. Final flow rate = Flow rate 1 + Flow rate 2 V/t =V/18 +V/24 Dividing the equation by V: 1/t =1/18 +1/24 t = [24 +18]/(18)(24) 1. t=42/(18)(24) t=10.2857 or 10 hours,17 mins and 8.5 seconds 2. D = r(t) D =20(4) = 80 km.,with the wind. D = r(5) = 80 r =80/5. =16 km/hr. Average speed = speed of plane in still air =[20+16]/2 = 18 km/hr

Answer 8

You do these problems by figuring how many tanks per hour each pipe can fill. tanks per hour + tanks per hour =total tanks per hour. So, for instance, the first pipe can fill 1/4 tank/hour. If you know the total tanks per hour for the two pipes, the reciprocal is hours per tank.

Answer 9

Continuing from hacksigntom's answer...

1/4x + 1/5x = 1

1/4 refers to 1/4 tank per hour

1/5 refers to 1/5 tank per hour

1 refers to one full tank


Comes out to:
9/20x = 1

x = 1/0.45, or 1 hour, 13 minutes, and 20 seconds
(might wanna recheck it to be sure though)

Answer 10

1/4x + 1/5x = 1

I might be wrong though since i'm doing this from memorization.