110 Speed Math for Kids
Test you rself
Try these problems in your head:
a) 531
- 297
b) 333 - 249
c) 4,537 - 388
For a) you simply add 300 and subtract 3:
531 + 300 is 831, minus 3 is 828
For b) you add 200, then add 50, and subtract 1:
333 + 200 is 533, plus 50 is 583, minus 1 is 582
For c) you add 400 and subtract 12:
4,537 plus 400 is 4,937, minus 12 is 4,925
ADDING FROM LEFT TO RIGHT
For most additions, if you are adding mentally, you should add
from left to right instead of from right to left as you are taught in
school.
How would you add these numbers in your head?
5,164 - 2,938
I would add 3,000, then subtract 100 to add 2,900. Th en I would
add 40 and subtract 2 to add 38.
To add 2,900 you would say, “Eight thousand and sixty-four,” then add
40 and subtract 2 to get “Eight thousand, one hundred and two.”