Idiot\'s Guides Basic Math and Pre-Algebra

Chapter 6: Decimals 69

The decimal fractions are written to the right of the decimal point. The first position after the
point is the tenths place. It imagines you broke a whole into ten parts, called tenths, and the digit
in that place shows how many of those parts you have. In our dollar and cents example, the 1 just
to the right of the decimal point is worth one tenth of a dollar, or in other words, a dime.

How many tenths can you have? You might not have any, in which case you could put a zero in
that place. If you had 1, or 2, or 3, or 4, or 5, or 6, or 7, or 8, or 9, that digit goes in the tenths place.
What if you have more than that? Ten tenths make 1 whole, so make groups of ten tenths, see how
many groups you have and put that number in the ones place. The leftovers, if any, will have to
be fewer than 10 tenths, so that digit goes in the tenths place. If you had 23 tenths, you’d have 2
groups of 10 tenths and 3 tenths left over, so that would be 2 ones and 3 tenths, or 2.3.

Of course, you might want to break the whole into smaller parts, so the next place to the right imag-
ines you break the whole into 100 parts, each called one hundredth. You can think of it as breaking
each tenth into ten parts, or breaking one whole into a hundred parts. You get the same thing.

The digit in the hundredths place tells you how many of those little pieces you have. The
number 4.05 says you have 4 ones and 5 hundredths.

WORLDLY WISDOM

Notice that all the places to the right of the decimal have a “th” at the end of their

names. That’s the signal that you’re talking about a fraction.

Do you have more than 9 of these hundredths? A group of 10 hundredths makes one tenth, so
count up how many groups you have and that goes in the tenths place, and what’s left over goes
in the hundredths place. You can think of the number 0.48 as 48 hundredths, or as 4 tenths and
8 hundredths.

If you had more than a hundred hundredths, you’d make a 1 from each group of 100. When you’ve
made all the groups of 100 you can, you can look for groups of 10 hundredths to make tenths, and
the leftovers would go in the hundredths place. If you had 793 hundredths, you’d have 7 groups of
100 hundredths, 9 groups of 10 hundredths, and 3 hundredths left over. That’s 7 ones, 9 tenths and
3 hundredths, or 7.93, seven and ninety-three hundredths.

1 tenth 10 hundredths

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