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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