Question

A certain pipe can fill a swimming pool in 2 hours; another pipe can fill it in 3 hours; a third pipe can fill it in 4 hours. Starting with an empty pool, if the second and
third pipe starts filling the pool and the first pipe is turned on exactly after 1 hour, how long will it take to fill in the pool?
312 hours
18/13 hours
1 hour
15/11 hours​

Answer 1

Answer:

1 hr

Step-by-step explanation:

it will take 1 hr to fill in the pool

Answer 2

Given:

✰ A certain pipe can fill a swimming pool in 2 hours.

✰ Another pipe can fill it in 3 hours.

✰ A third pipe can fill it in 4 hours.

✰ The second and third pipe starts filling the pool and the first pipe is turned on exactly after 1 hour.

To find:

✠ How long will it take to fill in the pool?

Solution:

Let the pipes be A,B,C.

Let the total working hours to fill the pool is x hours.

➛ In x hours A can fill it in x/2 hours

➛ In x hours B can fill it in x/3 hours

➛ In x hours C can fill it in x/4 hours

If B and C working together A joined after 1 hour exactly then the remaining hours of A to be worked = ( x - 1 )/2 hours

Total work be 1

➤ ( x/3 ) + ( x/4 ) + ( x-1 )/2 = 1

LCM of 2,3,4 is 12

➤ [ 4x + 3x + 6( x - 1 ) ]/12 = 1

➤ 7x + 6x - 6 = 1 × 12

➤ 13x - 6 = 12

➤ 13x = 12 + 6

➤ 13x = 18

➤ x = 18/13

∴ It will take 18/13 hours to fill in the pool.

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