felippemed wrote:

The figure above represents a rectangular tank. How many cubic centimeters of water are in the tank when the water level is 10 centimeters below the top of the tank?
(A) 12,672,000
(B) 13,824,000
(C) 126,720,000
(D) 138,240,000
(E) 1,267,200,000
Dear
felippemed,
I'm happy to respond.

This is a question crying out for
estimation!
First, we will estimate: it's about 1000 x 1000 x 100, which would be 100,000,000. Choices (A) & (B) are way to small, and choice (E) is way too big, but (C) & (D) are plausible. Right away, if we were shoot on time, we could guess from the two remaining answers, and our odds of advancing would be excellence.
Do not, do not, do not under any circumstances perform the multiplication. Here's another trick. Look at the final digit of each factor: 2 in the hundreds place, 6 in the tens place, and 1 in the tens place. Multiply these: we get 12, or in other words, a final digit of 2 in the ten thousands place. From this, we immediately see that the answer must be (C), not (D).
Does all this make sense?
Mike
_________________
Mike McGarry
Magoosh Test PrepEducation is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)