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SSC Selection Post 2020 PYQ — Question 63

SSC Selection Post - Matriculation Level 2020 - 10 Nov 2020 - Shift 1 • Quantitative Aptitude • Q63

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The average score of 84 students (boys and girls) in a test is 57. The ratio of the number of boys to that of girls is 10 : 11. The average score of boys is 20% less than that of girls. What is the average score of girls in the test?

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Correct answer: D

Explanation

The correct answer is option 4 i.e. 63.

 

Total parts = 10 + 11 = 21

Number of boys = (10/21) × 84 = 40

Number of girls = (11/21) × 84 = 44

Let average score of girls = x

Then, average score of boys = x – 20% of x = 0.8x

overall average = 

[(40×0.8x)+(44×x)84=57][ \frac{(40 × 0.8x) + (44 × x)}{84} = 57 ]

[⇒32x+44x84=57⇒76x84=57[ \Rightarrow \frac{32x + 44x}{84} = 57 \Rightarrow \frac{76x}{84} = 57 ⇒x=57×8476⇒x=478876=63]\Rightarrow x = \frac{57 × 84}{76} \Rightarrow x = \frac{4788}{76} = {63} ]