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SSC Selection Post 2019 PYQ — Question 56

SSC Selection Post - Graduation Level 2019 - 16 Oct 2019 • Quantitative Aptitude • Q56

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The average weight of some children in a group was 48.5 kg. When 6 students having average weight 50.4 kg left the group and 4 students having average weight 56.55 kg joined the group, then the average weight of the children in the group increased by 0.8 kg. The number of children, initially, in the group was

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Correct answer: C

Explanation

The correct answer is Option 3 i.e. 28.

Let initial number of children = x

Initial total weight = 48.5x

6 left (avg 50.4): lost = 302.4

4 joined (avg 56.55): gained = 226.2

New total = 48.5x − 302.4 + 226.2 = 48.5x − 76.2

New average = 49.3, new count = x − 2

48.5x−76.2x−2=49.3⇒48.5x−76.2=49.3x−98.6⇒22.4=0.8x⇒x=22.40.8=28\frac{48.5x - 76.2}{x - 2} = 49.3 \\ \Rightarrow 48.5x - 76.2 = 49.3x - 98.6 \\ \Rightarrow 22.4 = 0.8x \\ \Rightarrow x = \frac{22.4}{0.8} = 28