The longer base of a trapezoid is three times the shorter base. The nonparallel sides are congruent. The nonparallel side is 5 cm more that the shorter base. The perimeter of the trapezoid is 40 cm. What is the length of the longer base?
a. 15 cm

b. 5 cm

c. 10 cm

d. 21 cm

a. The two bases of the trapezoid are shown by x and 3x. The nonparallel sides are each x + 5. Setting up the equation for the perimeter will allow us to answer for x; x + 3x + x + 5 + x + 5 = 40. Simplify to 6x + 10 = 40. Subtract 10 from both sides; 6x = 30. Divide both sides by 6; x = 5. The longer base is shown by 3x. Using substitution, 3x or (3)(5) equals 15, the longer base. If you select b, you solved for the shorter base. If you select c, you solved for the nonparallel side. If you select d, the original equation was incorrect, x + x + 5 + 3x = 40.