C Meen's answer to Gwen Beatrice's Primary 6 Maths Data Analysis Singapore question.
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Date Posted:
5 years ago
Another way to see it is that the average of any number in the grid and the number opposite(for corner numbers it will be the number diagonally opposite) is equal to the middle number.
Opposite of 3 is 21, average of the two is 12.
Opposite of 4 is 20, average is also 12
Opposite of 5 is 19, average is also 12
Opposite of 11 is 13, average is also 12
So each of these pairs is equal to 2 x 12.
There are 8 times of 12. Add the middle number and it will be 9 times of 12.
If they gave you only info like the sum of all 9 numbers (or things like sum of two numbers diagonal of the middle number) this will come in useful to find the middle number
Opposite of 3 is 21, average of the two is 12.
Opposite of 4 is 20, average is also 12
Opposite of 5 is 19, average is also 12
Opposite of 11 is 13, average is also 12
So each of these pairs is equal to 2 x 12.
There are 8 times of 12. Add the middle number and it will be 9 times of 12.
If they gave you only info like the sum of all 9 numbers (or things like sum of two numbers diagonal of the middle number) this will come in useful to find the middle number
Thx
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