one pump can drain a pool in 10 min . when second pump is also used, the pool only takes 9 min to drain. How long would it take the second pump to drain if it were the only pump in use.

a. 90minutes b. 89minutes c. 4 14/9 minutes d. 1/90 minutes

Question

one pump  can drain a pool in 10 min . when second pump is also used, the pool only takes 9 min to drain. How long would it take the second pump to drain if it were the only pump in use.

a. 90minutes b. 89minutes c. 4 14/9 minutes d. 1/90 minutes

amistre64 · Answer

how much is "left in" after 1 minute?

amistre64 · Answer

helps if I read the question thru...

amistre64 · Answer

a + b = 9 minutes

a = 10 minutes

a:10  as a+b:9

9a = 10a + 10b

-a = 10b

a = -10b ??  does that make sense?

amistre64 · Answer

d...

a = 1/10 drained in one minute

a+b = 1/9 drained in a minute

1/10  +  b  = 1/9  per minute

b = 1/9  -   1/10

b = 10-9 /90

b = 1/90  per minute