Idea 21of 23Builds onThe little 1 is a ten moved upA zero holds an empty place
Line up the places in decimals
How do you add 12.5 and 3.75?
Today you'll discover
- why the decimal points line up
- where a zero helps
- how tenths regroup into ones
Think first12.5 + 3.75, lined up by place
What is 12.5 + 3.75?
Decide first, then press Next. Keep ones over ones and tenths over tenths.
12.5 above 3.75 in columns for tens, ones, tenths and hundredths, the decimal points in one line. Then the same numbers pushed to the right, the 5 tenths wrongly over the hundredths. Then a 0 fills the empty hundredths, 12.50, and the columns are added from the right: 16.25, with the check 16.25 − 3.75 = 12.50. The last step asks for 8 − 2.45.
See the whole ideathe big idea and the key word, in one place
The big idea
Line up decimals by place, so the decimal points line up; a zero can fill an empty place.
For exampleMoney works this way: $12.50 + $3.75 = $16.25. Dollars over dollars, cents over cents.
Key word
- decimal point
- the dot between the ones and the tenths
Ready to use it?
- Add and subtract decimals to hundredths, lined up by place.