Problem 4: The average weight of a group of boys and girls is 38 kgs. The average weight of the boys is 42 kgs, and that of girls is 33 kgs. If the number of boys is 25. find the number of girls.

Average Calculation 0

Problem 4: The average weight of a group of boys and girls is 38 kgs. The average weight of the boys is 42 kgs, and that of girls is 33 kgs. If the number of boys is 25. find the number of girls.

a) 10 b) 20 c) 15 d) 17

Solution:

Let the weight of 25 boys be w1,w2,w3,…………w25. Their average weight is 42kg

$\Rightarrow \frac{w1+w2+w3+......+w25}{25}=42$

Now suppose total weight of boys w1+w2+w3+…..+w25 = TwB (written shortly);

$\Rightarrow \frac{TwB}{25}=42$

$\Rightarrow TwB=42\times 25$

$\Rightarrow TwB=1050$

Similarly, supposing there are ‘y’ girls, then for girls we can write;

$\Rightarrow \frac{TwG}{y}=33$

$\Rightarrow TwG=33y$

But we are given that average weight of all girls and boys is 38;

$\Rightarrow \frac{Weight Of All Girls+Boys}{Number of All Girls+Boys}=38$

$\Rightarrow \frac{TwB+TwG}{25+y}=38$

$\Rightarrow \frac{1050+33y}{25+y}=38$

$\Rightarrow 1050+33y=38(25+y)$

$\Rightarrow 1050+33y=950+38y$

$\Rightarrow 1050-950=38y-33y$

$\Rightarrow 100=5y$

$\Rightarrow 20=y$

So, there are 20 boys.

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Problem 4: The average weight of a group of boys and girls is 38 kgs. The average weight of the boys is 42 kgs, and that of girls is 33 kgs. If the number of boys is 25. find the number of girls.

You may submit a MCQ or maths problem with solution tips here in the comment box below! If you could not solve anyone, you may submit a MCQ or maths problem without solution as well. We will try our level best to solve it for you! Cancel Reply

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Problem 4: The average weight of a group of boys and girls is 38 kgs. The average weight of the boys is 42 kgs, and that of girls is 33 kgs. If the number of boys is 25. find the number of girls.

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