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2016-02-08T23:19:16+08:00

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Given:
Area of trapezoid = 390 cm²
height = 15 cm
base1 = 20 cm

Find the length of the other base.

Area of a trapezoid = (a + b)/2 * h
390 cm² = (20 cm + b)/2 * 15 cm
2 (390 cm²) = 2 (20cm + b)/2 *15cm
780 cm² = (20cm + b)* 15cm
780 cm² / 15 cm = 20cm + b
52 cm = 20 cm + b
52 cm - 20 cm = b
32 cm = b
 
Area of trapezoid = (a+b)/2 * h
390 cm² = (20cm + 32cm)/2 * 15 cm
390 cm² = 52cm/2 * 15cm
390 cm² = (52 cm * 15 cm)/2
390 cm² = 780 cm²/2
390 cm² = 390 cm²

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