Arjun asked in Science & MathematicsMathematics · 8 years ago

# Average Weight question?

the average weight of pupils is 45 kg . 7 of them weight an average of 42 kg. what is the average weight of the remaining pupils?

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• Moon
Lv 7
8 years ago

How many pupils in total ......... ?

This is important.

Let us suppose there are total 10 people

Total weight of 10 people = average x number = 45 x 10 = 450

Total weight of known 7 people = average of 7 x 7 = 42 x 7 = 294

Total weight of the remaining (10-7= 3) people = 450 - 294 = 156

Average weight of the 3 people = total / 3 = 156/3 = 52 ............................ answer

...........

• ?
Lv 5
8 years ago

You can't do this unless you know how many are remaining. If there is only one pupil remaining then his weight is 66 kg. If there are 3 pupils remaining then their average weight is 52 kg. It will change depending on how many pupils are remaining.

• 8 years ago

If there were 7 students remaining who had an average mass of 48kg that would make it work.

((7 x 48) + (7 x 42)) / 14 = 45

as required

• 8 years ago

hmmm