Homework Help: math

Posted by Brigitta on Thursday, January 31, 2013 at 10:56pm.

The longer base of an isosceles trapezium is 20 cm, its legs are 10cm. The legs of the trapezium are extended by 8 cm long to gain an isosceles triangle.Find the shorter base of the trapezium. Please help me:)

math - Reiny, Thursday, January 31, 2013 at 11:51pm
did you make a sketch?

I have a large isosceles triangle containing your original trapezium
The sides of the triangle are made up of the segments 10 and 8 for a total length of 18 each

I see a smaller isosceles triangle contained and similar to a larger isosceles triangle
let the smaller base be x

remember the sides of similar triangles are in the same ratio
so....
x/8 = 20/18
x = 8(20/18) = 80/9 or appr. 8.89 cm
math - Brigitta, Friday, February 1, 2013 at 11:03pm
thank u so much!:)

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