Q.In triangle \( \triangle ABC \), a line parallel to side BC intersects sides AB and AC at points D and E respectively. If \( AB = 20 \) cm and \( BD = 14 \) cm, then what is the ratio \( DE : BC \)? (a) 7:10 (b) 5:17 (c) 3:10 (d) 7:17
Answer: C
In triangle \( \triangle ABC \), DE is parallel to BC. ∴ \( \frac{AD}{AB} = \frac{DE}{BC} \) Or, \( \frac{AB - BD}{AB} = \frac{DE}{BC} \) Or, \( \frac{20 - 14}{20} = \frac{DE}{BC} \) Or, \( \frac{DE}{BC} = \frac{6}{20} = \frac{3}{10} \) ∴ \( DE : BC = 3 : 10 \)
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