Question

A group of boys has an average weight of 36 kg. One boy weighing 42 kg leaves the group and another boy weighing 30 kg joins the group. If the average now becomes 35.7 kg, then how many boys are there in the group?

Answer 1

the number of boys in the group is 40

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Answer 2

There are 40 boys in the group.

Step-by-step explanation:

Let the number of boys in the group be 'n'.

Average of group of boys = 36 kg

So, it becomes,

$\dfrac{\sum x}{n}=36\\\\\sum x=36n$

If one boy weighing 42 kg leaves the group and another boy weighing 30 kg joins the group.

$\dfrac{\sum x-42+30}{n}=35.7\\\\\sum x-12+35.7n\\\\36n-12=35.7n\\\\36n-35.7n=12\\\\0.3n=12\\\\n=40$

Hence, there are 40 boys in the group.

# learn more:

How to subtract 35.7 kg 23.5kg

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