186 Speed Math for Kids
6 × 10 = 60
6 × 7 = 42
60 + 42 = 102 Answer
How about 6 times 27?
Six times 20 is 120 (6 × 2 × 10 = 120). Six times 7 is 42. Th en, 120 +
42 = 162. Th e addition is easy: 120 plus 40 is 160, plus 2 is 162.
Th is is much easier than working with positive and negative numbers.
It is easy to multiply a two-digit number by a one-digit number.
For these types of problems, you have the option of using 60, 70
and 80 as reference numbers. Th is means that there is no gap in the
numbers up to 100 that are easy to multiply.
Let’s try a few more for practice:
7 × 63 =
You could use two reference numbers for this, so we will try both
methods.
First, let’s use direct multiplication.
7 × 60 = 420
7 × 3 = 21
420 + 21 = 441
Th at wasn’t too hard.
Now let’s use 10 and 70 as reference numbers.
(10 × 7) 7 × 63 =
–3
–7
–21
brent
(Brent)
#1