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SSC CGL 2020 PYQ — Question 5

SSC CGL Tier II - Quant - 15 Nov 2020 • Quantitative Aptitude • Q5

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Given that △DEF~△ABC. IF the area of △ABC is 9 cm2 and that of △DEF = 12 cm2 and BC = 2.1 cm, then the length of EF is :

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Correct answer: B

Explanation

The correct answer is option 2 i.e.  7√35\frac{7√3}{5}cm

Concept of Similiarity

When two triangles are similar, the lenght of the corresponding side ratios are in square.

Understanding

(area of ΔABC/area of ΔDEF) = (AB/DE)2 = (BC/EF)2 = (AC/DF)2

Application

Let EF = x

BC = 2.1 Given

According to question

(9/12) = (2.1/x)2

Upon solving

x2 = (7 × 7 × 3)/25

x = (7√3)/5

EF = (7√3)/5 cm