Question

Ten pipes ar fitted to a tank. Some of these are filling pipes while the others are emptying pipes. Each filling pipe can fill the tank in 8 hours. Each of emptyting pipe can empty it in 16 hours . All the pipes are opened simultaneously. The tank takes 2 hours to be filled. How many filling pipes are fitted to it? Choose the correct answer from the following option.
A. 8
B. 7
C. 9
D. 6

Answer 1

Let the number of filling pipes be f.
Number of emptying pipes=10-f
Part of the tank filled each hour `=(1)/(2)`
`:.(1)/(8)f-(1)/(10)(10-f)=(1)/(2)`
`(1)/(8)f-(5)/(8)+(f)/(16)=(1)/(2)`
`(3f)/(16)=(9)/(8)rArrf=6`