16Hit1600
Geometry and TrigonometryHardSide of a similar triangle from an area ratio

Geometry and Trigonometry practice question

Triangle ABC is similar to triangle DEF, and the area of triangle ABC is 9 times the area of triangle DEF. If AB = 12, what is the length of the corresponding side DE?

Answer: 4

Areas scale by the square of the length ratio, so lengths are in the ratio 3 : 1 and DE = 12/3 = 4.

Common wrong answers

If you answered 36
36 multiplies 12 by 3.
If you answered 108
108 multiplies 12 by 9.
If you answered 1.33
1.33 divides 12 by 9, using the area ratio as a length ratio.

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