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