22 Speed Math for Kids
+3
+5
10 13 × 15 =
As before, we now go crossways. Th irteen plus 5 or 15 plus 3 is 18.
We write 18 after the equals sign.
+3
+5
10 13 × 15 = 18
We then multiply the 18 by the reference number, 10, and get 180.
(To multiply a number by 10 we add a 0 to the end of the number.)
One hundred and eighty is our subtotal, so we write 180 after the
equals sign.
+3
+5
10 13 × 15 = 18 0
For the last step, we multiply the numbers in the circles. Th ree times
5 equals 15. Add 15 to 180 and we get our answer of 195. Th is is
how we write the problem in full:
+3
+5
10 13 × 15 = 180
- 15
195 Answer
If the number we are multiplying is above the reference
number, we put the circle above. If the number is below
the reference number, we put the circle below.
If the circled number is above, we add diagonally.
If the circled number is below, we subtract diagonally.