alleryTriangles ABC and DEF are similar with AB = 4 cm, BC = 5 cm, CA = 6 cm and EF = 7.5 cm. The perimeter of triangle DEF is
A18 cm
B22.5 cm
C20.5 cm
D25 cm
Answer & Solution
Correct answer: B. 22.5 cm
1. Side BC corresponds to EF, so scale factor = 7.5 / 5 = 1.5.
2. Perimeter of ABC = 4 + 5 + 6 = 15 cm.
3. Perimeter of DEF = 15 × 1.5 = 22.5 cm.
_Source: syllabus Mathematics, Ch 6 "Triangles", §6.4_
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