Question

The areas of two similar triangles and are 25cm2 and 49 cm2 respectively. If QR = 9.8 cm, find BC.​

Answer 1

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$\frac{arABC}{arPQR}$ = $\frac{25}{49}$

In two similar triangles, the ratio of their areas is the square of the ratio of their sides

($\frac{BC}{QR}$ )^2 = $\frac{25}{49}$

$\frac{BC}{QR}$ = $\frac{5}{7}$

$\frac{BC}{9.8}$ = $\frac{5}{7}$

BC = $\frac{5}{7}$ × 9.8

BC = 7