Q1 of 186 Page 229

ΔABC ~ ΔDEF and their areas are respectively 64 cm2 and 121 cm2. If EF = 15.4 cm, find BC.


We know that if two triangles are similar then the ratio of their areas is equal to the ratio of the squares of their corresponding sides.





More from this chapter

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18

Two chords AB and CD of a circle intersect at a point P outside the circle. Prove that

(a) ΔPAC ~ ΔPDB (b) PA • PB = PC • PD.


 19

In a right triangle ABC, right-angled at B, D is a point on hypotenuse such that BD ⊥ AC. If DP ⊥ AB and DQ ⊥ BC then prove that (a) DQ2 = DP • QC (b) DP2 = DQ • AP.

 2

The areas of two similar triangles ABC and PQR are in the ratio 9 : 16. If BC = 4.5 cm, find the length of QR.

 3

ΔABC ~ ΔPQR and ar (ΔABC) = 4ar (ΔPQR). If BC = 12 cm, find QR.