Question

One valve drains a pool in 2 hours, and another drains it in 9 hours. How long will it take to drain the pool with both valves open at the same time? Round to the nearest tenth.




4.5 hours

7 hours

1.6 hours

0.6 hours

Answer 1

let A drain in 2 hrs..

So A drains in unit time = 1/2
and B drains in unit time = 1/9

so together they will drain in A + B
= 1/2 + 1/9
= (9 + 2 ) / 18
= 18/11

= 1.63 = 1.6 hrs...

Answer 2

u understood ??

Answer 3

yeah i got it

Answer 4

great..