amanvermagmat wrote:
Pipes X and Y are inlet pipes attached to a tank, and these pipes fill the tank at their own respective individual constant speeds. When the tank was empty, pipe X was opened at 10 am and kept open until it filled the tank to its 40% capacity. After that, immediately pipe X was closed and simultaneously pipe Y was opened and kept open until the tank was filled completely. If these are the only two pipes attached to the tank, what percentage of the tank was filled by 2 pm on the same day?
(1) Pipe X was closed at 12 noon.
(2) Pipe X and pipe Y, if opened together, can fill 30% of the tank in 1 hour.
Before diving into statements, we are given that from 10AM ~ T, the X pipe was open and 40% of the tank was filled. From T ~ 2PM, the Y pipe was open, and we are asked to find how much the tank is filled in percentage.
Statement 1. It says that the Pipe X was turned off at Noon. -> X pipe was on for 2 hours -> each hour 20% of the tank filled. But this is it. No information about Y. INS.
Statement 2. It says that when X and Y is on together, they fill 30% together. .... this statement alone is no good since, with this alone, we do not know each rate for pipe X and Y
Together? : Since we know hourly rate for X, from statement 1, we can find that Y fill 10% / hour from information given in Statement 2.
As such, the total tank filled : 60% (20 * 2 + 10 * 2)
Answer: C