The question is from the topic triangles. It tests the understanding of the basic concepts triangles. CAT Geometry questions are heavily tested in CAT exam. Make sure you master Geometry problems.
Question 43: In the below figure, ΔABC is right angled and AC = 100 cm. Also, AD = DE = EF = FC. Find the value of: BD2 + BE2 + BF2 (in cm2)
E is the midpoint of hypotenuse AC so, BE = 1/2 ∗ AC=50 cm
Now, applying Apollonius’s theorem on ΔABE
=> AB2 + BE2 = 2 * (BD2 + AD2)
=> AB2 + 502 = 2 * (BD2 + 252)……….(1) (As, AD = DE = EF = FC = 25 cm)
Similarly, in ΔBEC,
=> BC2 + BE2 = 2 * (BF2 + EF2)
=> BC2 + 502 = 2 * (BF2 + 252)………..(2)
Adding (1) and (2),
=> AB2 + BC2 + 2 * 502 = 2 * (BD2 + BF2 + 2 * 252)
=> AC2 + 2 * 502 = 2 * (BD2 + BF2) + 4 * 252 (As, AB2 + BC2 = AC2)
=> 1002 + 2 * 502 – 502 = 2 * (BD2 + BF2)
=> 1002+ 502 = 2 * (BD2 + BF2)
=> (10,000 + 2500)/2 = (BD2 + BF2)
=> 12500/2 = BD2 + BF2
Therefore, BD2 + BF2 = 6250
=> BD2 + BF2 + BE2 = 6250 + 502 = 6250 + 2500 = 8750 cm2
The question is "Find the value of: BD2 + BE2 + BF2 (in cm2)"
Choice C is the correct answer.
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