Tiger, please advise what is wrong in my calculations:

Total work is 100,000 litres:

a-rate of A hose

b-rate of B hose

100,000/a- time for A hose alone to fill the pool

100,000/b- time for B hose alone to fill the pool

We are asked to find 100,000/(a+b),

which reduces to the question what is a+b. in 1) we are given that after filling a part (1/3 of pool) B worked alone and for a given period of time filled the pool in 22 hours. , so we can calculate b.

we are not provided how much time did it take A and B hose to fill 1/3 of pool, or 33,333 litres., so the 33,333/(a+b)=x hours. hence not sufficeint.

in 2) we are told that it will take hose A 17 hours to fill 50,000 litres of pool, we can calculate a.

50,000/(a+b)=y hours, not sufficient. not suff.

1)& 2) both rates are provided, thus sufficeint to calculate total amount of time. (a+b) , hence C.

_________________

Audaces fortuna juvat!

GMAT Club Premium Membership - big benefits and savings