154 Speed Math for Kids
Twenty-nine is less than 30 and 30 divides into 239 almost 8 times,
as it is only 1 less than 240, which is exactly 8 times 30. So we
multiply 8 times 29 to get 232, which is a valid answer.
Had we not seen this and chosen 7 as our answer, our remainder
would have been too large.
Seven times 29 is 203. Subtract 203 to fi nd the remainder.
239 – 203 = 36
Th is is higher than our divisor, so we know we have to raise the last
digit of our answer.
What if we are dividing by 252? What do we round it off to? Two
hundred is too low and 300 is too high. Th e easy way would be to
double both the number we are dividing and the divisor, which
won’t change the answer but will give us an easier calculation.
Let’s try it.
2,233 ÷ 252 =
Doubling both numbers, we get 4,466 ÷ 504. We now divide by
500 (5 × 100) for our estimates and correct as we go.
8 r434
504 4,466
4,032
434
We divide 4,466 by 500 for our estimate. We divide using factors
of 100 × 5:
4,466 ÷ 100 gives 44
44 ÷ 5 gives 8 (8 × 5 = 40)
Now, 8 × 504 = 4,032, subtracted from 4,466 gives a remainder of
- If the remainder is important (we are not calculating the answer