IN YOUR MATHS LESSON

Why not check your sums by this fascinating method using digit sums.

- Suppose you want to check that the simple

addition sum below is correct.

4 3

3 2 +

___

7 5

We find the digit sums of 43, 32 and 75 and check

that the first two digit sums add up to the third digit sum.

4 3 7

3 2 + 5 +

___ _

7 5 3

The digit sums are shown on the right and

7 + 5 = 3 is correct in digit sums because

7 + 5 = 12 = 3 (1 + 2 = 3)

This indicates that the answer is correct.

All sums, even the most complex, can be checked in this way.

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In Your Maths Lesson

It is worth noting (in case you want to check

subtraction sums using the nine-point circle) that in

digit sums 7-5=2, 6-6=0 and so on, but 3-4=8.

You can see this on the circle by starting at 3 and

going 4 jumps backwards round the circle.

Or, alternatively you can add 9 to the 3 so that 3-4

becomes 12-4, which is 8.

The advancement

and perfection of

Mathematics are

intimately

connected with the

prosperity of the

state

and perfection of

Mathematics are

intimately

connected with the

prosperity of the

state

NAPOLEON