126 Speed Math for Kids
Th ree from 9 is 6. Five from 9 is 4. Nine from 9 is 0. Four from 10
is 6.
Th e answer is 36,406.
You could do the calculation off the top of your head. You would
call out the answer, “Th irty-six thousand, four hundred and six.” Try
it. With a little practice you can call out the digits without a pause.
You may fi nd it easier just to say, “Th ree, six, four, oh, six.” Either
way it is very impressive.
Test you rself
Try these for yourself:
a) 10,000 – 2,345 b) 60,000 – 41,726
You would have found the answers are:
a) 7,655 b) 18,274
Subtracting smaller numbers
If the number you are subtracting is short, then add zeroes before
the number you are subtracting (at least mentally) to make the
calculation.
Let’s try 45,000 – 23:
4 5 0 0 0
- 0 0 2 3
4 4 9 7 7
You extend the zeroes in front of the subtrahend (the number being
subtracted) as far as the fi rst digit that is not a 0 in the top number.
You then subtract 1 from this digit. Five minus 1 equals 4.
Subtract each successive digit from 9 until you reach the fi nal digit,
which you subtract from 10.