# calculus ( help please )

posted by
**mehak**
.

The troough down the center of the ccattle barn is 40 cm wwide at thhe top and 20 cm at the botttom .it is 30 cm deep and 8 m long . It iis filled at a rate of 10 dm3/min. What is the rate of rise of water level .

I tried it and me ans is pretty close but not exact so just wanted if somebidy had any ideas?