100 Speed Math for Kids
Now let’s try using reference numbers of 10 and 80.
+3
(10 × 8) 13 × 76 =
–4
Multiply 3 times 8 to get 24. Write 24 in a circle above the 3. Add
24 to 76 to get 100. Multiply your answer by the base reference
number of 10 to get 1,000.
Th e problem now looks like this:
+24
+3
(10 × 8) 13 × 76 = 1,000
–4
Multiply 3 times minus 4 to get minus 12. Subtract 12 from 1,000
to get your answer, 988. (To subtract 12, subtract 10, then 2.)
+24
+3
(10 × 8) 13 × 76 = 1,000
–4
- 12
988 Answer
Let’s try another option; let’s use 10 and 75 as reference numbers.
+3
+1
(10 × 7½ ) 13 × 76 =