Question

Triangle ADB is similar to Triangle EDC. Find CB.
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Answer 1

Explanation:

If triangles ADB and EDC are similar, then corresponding sides are proportional, from which we conclude:

BC/CD = AE/ED

BC / 21 = 6 / 18

Multiply by 21 on both sides,

BC = 6*21 / 18 = 21 / 3 = 7 units.

(note: Length BC is the same as length CB).