76 Part 1: The World of Numbers
Start from the right side and count to the left. The 2 in 62 is one digit, the 6 is a second, but there
must be 4 digits to the right of the decimal point so place zeros for the third and fourth, giving an
answer of 3.1 v .002 = .0062.
Once again, it’s traditional to put a zero in the ones place, so 3.1 v 0.002 = 0.0062.WORLDLY WISDOM
Just as you can add trailing zeros at the right end of a decimal without changing
its value, you can add zeros at the left of a number. 87 and 087 describe the same
number, but with whole numbers you don’t need that zero in front. When you’re
placing a decimal point you might. If you run out of digits, add zeros to the left end of
the number until you have enough places.To multiply decimals:- Multiply the factors without regard to the decimal points.
- Count the number of digits that follow the decimal point in each factor.
- Add those counts to find the number of digits after the decimal point in the product.
- Start from the right end of the product and count to the left until there are the required
number of digits after the decimal point.
Just as multiplication of decimals is based on multiplication of whole numbers, with a rule for
placing the decimal point, the division of decimals is based on whole number long division. But
again, there will be some extra rules about decimal points. Let’s sneak up on it a little at a time.
To divide a decimal by a whole number, do your division as though both numbers were whole
numbers, but then let the decimal point rise straight up into the quotient. Suppose you want to
divide 54.96 z 12. You’re going to divide a number close to 55 by 12. 12 v 4 = 48, and 12 v 5 =
60, so your quotient should be between 4 and 5.
Divide as if you were dividing 5,496 by 12, and for now, just let the decimal point sit between the
4 and the 9. When you’re done dividing, let the decimal point f loat straight up, and it will land
right after the 4 in the quotient, giving you an answer of 4.58.)
12 54.96
48
69
60
96
964.58