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
