Hi Okigbo,

Machine X & Y produce identical bottles at different constant rates. Machine X, operating alone for 4 hours filled part of a production lot; then Machine Y operating alone for 3 hours filled the rest of the lot. How many hours would it take Machine X operating alone to fill the entire lot?

1. Machine X produces 30 bottles / min
2. Machine X produced twice as many bottles in 4 hours as Machine Y produced in 3 hours

From statement 1, we will be able to compute how many bottles X made in 4 hours but will not know how many Y made to complete the task. Hence, we will still not know the quantity of the full lot, and so will be unable to ascertain how long it would take X fill it. Insufficient.

From statement 2, we know that X did two out of three parts of the full job in 4 hours, and hence we would be able to compute how long it would take X to do the entire job (6 hours). Sufficient.

I would choose B.