Question

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

Answer 1

It is given that Δ ABC ~ Δ DEF.
Therefore, ratio of the areas of these triangles will be equal to the ration of squares of their corresponding sides.  

`(ar (Δ ABC))/(ar (Δ   DEF))=(BC^2)/(EF^2)` 

Let BC be X cm. 

⇒ `64/121=x^2/(15.4)^2` 

⇒` x^2=(64xx15.4xx15.4)/121` 

⇒ `x= (sqrt(64xx15.4xx15.4))/121` 

= `(8xx15.4)/11` 

= 11.2
Hence, BC = 11.2 cm