Decimal Subtraction Practice
Work on decimal differences, from matching tenths to subtraction that crosses several empty places. Choose a difficulty and pick the result from four answers. Each generated question gives immediate checking and an explanation, with a chance to retry before continuing. You will meet whole numbers, unequal decimal lengths, and regrouping questions. Start with the examples here if you tend to lose track of a borrowed unit or leave out a zero in the answer.
Start decimal subtraction practiceHow to subtract decimals
Write the number you are subtracting underneath the starting number, with the decimal points aligned. Keep units in the units column and each fractional place in its corresponding column. Unlike addition, the order of the two numbers matters. The calculation 7.8 − 3.2 asks how much remains after taking 3.2 from 7.8, not the other way around.
Fill any empty decimal places in the starting number with zeros. If the problem is 15 − 6.47, write 15 as 15.00. This makes the hundredths and tenths visible before you begin. It also shows that the decimal point in a whole number sits immediately after its units digit. Adding these zeros changes the notation without adding any value.
Begin at the right. When the upper digit is large enough, subtract normally. When it is smaller, exchange one unit from the column to its left for ten units of the current place. For example, one tenth can be exchanged for ten hundredths. Reduce the donating digit by one and add ten to the digit receiving the exchange.
Regrouping across a zero takes more than one exchange. In 15.00 − 6.47, exchange one unit for ten tenths. Then exchange one of those tenths for ten hundredths. The fractional part now contains nine tenths and ten hundredths. Subtract seven hundredths, then four tenths, while keeping track of the unit already exchanged. Write the adjusted digits above the original ones if that helps.
Bring the decimal point straight down into the answer. Keep zeros that hold an internal place, such as the zero in 2.03. Finally, check the difference by addition: the result plus the amount subtracted must recover the starting number. This reverse check is particularly useful after borrowing across zeros because it checks every adjusted column together.
Worked examples
1. 7.8 − 3.2
- Subtract the tenths: 8 − 2 = 6.
- Subtract the units: 7 − 3 = 4.
4.6
2. 15.00 − 6.47
- Regroup one unit into ten tenths, then one tenth into ten hundredths.
- 10 − 7 = 3 hundredths and 9 − 4 = 5 tenths.
- The remaining whole part is 14. Subtract 6 to leave 8.
8.53
Common mistake: skipping placeholder zeros
Starting 15 − 6.47 without writing 15.00 makes it easy to borrow from the wrong place. Show the two empty fractional places first, then record each exchange.
Questions about decimal subtraction
- How do you subtract decimals with different decimal places?
- Align the decimal points and add zeros to the shorter fractional part. Then subtract by columns, beginning at the right.
- How do you subtract a decimal from a whole number?
- Write the whole number with a decimal point and enough zeros. For example, 8 − 2.36 becomes 8.00 − 2.36 = 5.64.
- What happens when you need to borrow across the decimal point?
- Exchange one unit for ten tenths. The same place value relationship applies on both sides of the decimal point.