J's answer to lahari gowni's Primary 1 Maths Singapore question.
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Total of 4 numbers = 25 x 4 = 100
Total of 5 numbers = 27 x 5 = 135
5th number = 135 - 100 = 35
Alternative approach :
The first 4 numbers have their average increased by 2. That is a total increase of 4 x 2 = 8.
This means that the 5th number has to be decreased by 8 to become 27.
Add back the 8, 27 + 8 = 35
Total of 5 numbers = 27 x 5 = 135
5th number = 135 - 100 = 35
Alternative approach :
The first 4 numbers have their average increased by 2. That is a total increase of 4 x 2 = 8.
This means that the 5th number has to be decreased by 8 to become 27.
Add back the 8, 27 + 8 = 35
Date Posted:
4 years ago
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