Definition
Decimal subtraction
Decimal subtraction finds a difference by subtracting numbers written in decimal notation, matching each place value with the same place value.
What it means
Line up the decimal points so matching places are together. Write a trailing zero when it helps show a missing place. If one place does not have enough to subtract, regroup one unit from the place to its left as ten units of the current place.
Remember it
Match the places before finding what is left or how far apart the values are.
Example
8.30 − 2.47 = 5.83. Regroup 1 tenth as 10 hundredths, then regroup 1 one as 10 tenths. Now subtract by place: 10 − 7 hundredths = 3 hundredths, 12 − 4 tenths = 8 tenths, and 7 − 2 ones = 5 ones.
Watch for
Writing 8.3 as 8.30 does not add value; it only makes the hundredths place available for the written method.
Common mix-up
Do not subtract the smaller visible digit from the larger one in each column. Keep the order of the two numbers and regroup when needed.
Exact meaning
Decimal subtraction subtracts numbers written in decimal notation to find a difference. Ones are subtracted from ones, tenths from tenths, hundredths from hundredths, and regrouping follows base-ten place value.