Last Updated on May 4, 2023
GMAT OFFICIAL GUIDE PS
Solution:
Although this problem may seem confusing based on the description of the shape, we must keep in mind that the diagram provided is simply a trapezoid. So when we are asked to determine the area of the “cross section of the rudder,” this really means “What is the area of the trapezoid?”
The formula for the area of a trapezoid is:
area = (base 1 + base 2) x height/2
The two bases are given as 2 feet and 5 feet. Because the height is always perpendicular to the base, the height of this particular trapezoid is the side that begins at A and ends at the right angle located at the bottom right of the figure. We don’t know this value, so we must calculate it. We could use the Pythagorean Theorem to determine the height, but instead we note that we have a 5-12-13 right triangle, where the unknown side (or the height) is 12.
We can now substitute the values for the two bases (2 and 5) and the height (12) into our area equation.
area = (base 1 + base 2) x height/2
area = (2 + 5) x 12/2
area = 7 x 6
area = 42
Answer: C
