Multiplying Decimals 79
We write down the problem as it is, but when we are working it out,
we ignore the decimal points.
+2
+4
10 1.2 × 1.4 =
Although we write 1.2 × 1.4, we treat the problem as:
12 × 14 =
We ignore the decimal point in the calculation; we calculate 12 plus
4 is 16, times 10 is 160. Four times 2 is 8, plus 160 is 168.
Th e problem will look like this:
+2
+4
10 1.2 × 1.4 = 160
- 8
168 Answer
Our problem was 1.2 × 1.4, but we have calculated 12 × 14, so
our work isn’t fi nished yet. We have to place a decimal point in the
answer. To fi nd where we put the decimal, we look at the problem and
count the number of digits after the decimals in the multiplication.
Th ere are two digits after the decimals: the 2 in 1.2 and the 4 in 1.4.
Because there are two digits after the decimals in the problem, there
must be two digits after the decimal in the answer. We count two
places from the right and put the decimal between the 1 and the 6,
leaving two digits after it.
1.68 Answer
An easy way to double-check this answer would be to approximate.
Th at means, instead of using the numbers we were given, 1.2 × 1.4,
we round off to 1.0 and 1.5. Th is gives us 1.0 times 1.5, which is 1.5,
so we know the answer should be somewhere between 1 and 2. Th is