Question

Two similar triangles ABC and PQR have their areas 25 cm² and 49 cm² respectively. If QR = 9.8 cm, find BC.

Answer 1

Given, ΔABC ∼ ΔPQR

ar(ΔABC) = 25 cm²,

ar(ΔPQR) = 49 cm²

And QR = 9.8 cm

`(ar(ΔABC))/(ar(ΔPQR)) = ((BC)/(QR))^2`

⇒ `25/49 = ((BC)/(QR))^2`

⇒ `5/7 = "BC"/"QR"`   ...(Taking square root)

⇒ BC = `5/7` × QR

⇒ BC = `5/7` × 9.8

⇒ BC = 7 cm