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SSC Selection Post 2019 PYQ — Question 68

SSC Selection Post - Matriculation Level 2019 - 15 Oct 2019 • Quantitative Aptitude • Q68

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The average weight of certain number of children in a group was 27 kg. if 12 students of average weight 28.5 kg joined the group, then the average weight of all the children increased by 0.45 kg. The number of children, initially, in the group was:

 


 

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Correct answer: A

Explanation

The correct answer is Option 1 i.e. 28.

Let initial children = x

27x+12×28.5x+12=27.45\frac{27x + 12 \times 28.5}{x + 12} = 27.45

⇒27x+342x+12=27.45⇒27x+342=27.45x+329.4\Rightarrow \frac{27x + 342}{x + 12} = 27.45 \Rightarrow 27x + 342 = 27.45x + 329.4

⇒12.6=0.45x⇒x=12.60.45=28\Rightarrow 12.6 = 0.45x \Rightarrow x = \frac{12.6}{0.45} = 28