Question

Two inlet pipes a and b can fill an empty cistern in 22 and 33 hours respective.they are switched on together but pipe b had to be closed 7 hours before the cistern was full.how many hours in all did it take the two pipes to fill the cistern

Answer 1

Answer:

13.2 hrs

Step-by-step explanation:

1/22+1/33=5/66

=1/13.2

therefore the answer is 13.2 hrs

Answer 2

Answer: It takes $10\dfrac{2}{5}$ hours by the two pipes to fill the cistern.

Step-by-step explanation:

Since we have given that

Number of hours first inlet pipe takes = 22 hours

Number of hours second inlet pipe takes = 33 hours

Number of total units = L.C.M. of 22 and 33 = 66

Efficiency of first inlet pipe = $\dfrac{66}{22}=3\ units$

Efficiency of second inlet pipe = $\dfrac{66}{33}=2\ units$

Since, pipe B had to closed 7 hours before the cistern was full.

So, number of units he fill in 7 hours is given by

$2\times 7=14\ units$

Remaining units would be

$66-14=52\ units$

So, Number of hours it takes the two pipes to fill the cistern is give by

$\dfrac{52}{2+3}=\dfrac{52}{5}=10\dfrac{2}{5}\ hours$

Hence, it takes $10\dfrac{2}{5}$ hours by the two pipes to fill the cistern.