The area of a trapezoid is h(b1 + b2), where h is the altitude, and b1 and b2 are the lengths of the parallel bases. If a trapezoid has an altitude of 5 inches, an area of 55 square inches, and one base 13 inches long, what is the length, in inches, of its other base?
F. 9.0
G. 16.8
H. 19.4
J. 45.0
K. 97.0
謎底:F
【剖析】The correct answer is F. Substituting into the formula, 55 = (5)(13 + b),so 110 = 5(13 + b), 110 = 65 + 5b, 5b = 45, b = 9.