The midline of the trapezoid is 9, and one of the bases is 7. Find another foundation.

A trapezoid is a convex quadrilateral in which two sides are parallel and the other two are not parallel.

Given: trapezoid, l – middle line of the trapezoid, l = 9; a and b are the bases of the trapezoid, a = 7.

Find: base b.


The middle line of the trapezoid is parallel to the bases and equal to their half-sum.

l = (a + b): 2; a + b = l * 2; b = l * 2 – a; b = 9 * 2 – 7 = 18 – 7 = 11.

Answer: another base of the trapezoid 11.

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