46 Speed Math for Kids
We put 3 and 11 above 23 and 31:
+3 +11
20 23 × 31 =
Th ey are 3 and 11 above the reference number, 20. Adding diagonally,
we get 34:
31 + 3 = 34
or
23 + 11 = 34
We multiply this answer by the reference number, 20. To do this, we
multiply 34 by 2, then multiply by 10.
34 × 2 = 68
68 × 10 = 680
Th is is our subtotal. We now multiply the numbers in the circles (3
and 11):
3 × 11 = 33
Add this to 680:
680 + 33 = 713
Th e calculation will look like this:
+3 +11
20 23 × 31 = 34
680
- 33
713 Answer
We check by casting out the nines: