Answers

2016-01-27T16:39:36+08:00
I use this equation that I can share where:
b = base₁ (the length of the base on the given)
b₂ = base₂ (the base you needed)
a = area of the trapezoid
h = height


b_2= \frac{2a}{h} -b\\b_2= \frac{2(390cm^2)}{15cm} -20cm\\b_2= \frac{780cm^2}{15cm}-20cm \\b_2=52cm-20cm\\b_2=32cm

Therefore, the answer is 32 cm.
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