152 Speed Math for Kids
425
29 12345
116XX
74
58
165
145
20r
Our answer is 425 with 20 remainder. Th e calculation is done. Our
only real division was by 3.
Long division is easy if you regard the problem as an exercise with
factors. Even though we are dividing by a prime number, we make
our estimates by rounding off and using factors.
Th e general rule for standard long division is this:
Round off the divisor to the nearest ten, hundred
or thousand to make an easy estimate.
If you are dividing by 31, round off to 30 and divide by 3 and 10.
If you are dividing by 87, round off to 90 and divide by 9 and 10.
If you are dividing by 321, round off to 300 and divide by 3 and
100.
If you are dividing by 487, round off to 500 and divide by 5 and
100.
If you are dividing by 6,142, round off to 6,000 and divide by 6
and 1,000.
Th is way, you are able to make an easy estimate and then proceed
in the usual way.
brent
(Brent)
#1