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In triangle ABC right-angled at B, BD is perpendicular to AC. If AB = 5 cm and BC = 12 cm, then BD equals
A12/5 cm
B13/12 cm
C5/12 cm
D60/13 cm
Answer & Solution
Correct answer: D. 60/13 cm
1. Area of triangle ABC = 1/2 × AB × BC = 1/2 × 5 × 12 = 30 sq cm.
2. AC by Pythagoras = square root of (25 + 144) = 13 cm.
3. Area also equals 1/2 × AC × BD = 1/2 × 13 × BD. So BD = 60/13 cm.
_Source: NCERT Class 10 Mathematics, Ch 6 "Triangles", §6.5_
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