Fractions, decimals and percentsGrade 5
Multiplying decimals by whole numbers worksheets
The generator prints one-line problems such as 3.46 × 4 with a blank for the product. Choose one, two or three decimal places and the number of problems, then print with an answer key or save a PDF.
- Fresh problems every time
- Answer key on its own page
- Print or PDF, Letter or A4
- Free, no sign-up
On this page
Whole-number multiplication with one extra step
Multiplying a decimal by a whole number is ordinary multiplication followed by a decision about where the decimal point goes. A student who is comfortable with multi-digit multiplication can usually pick this up quickly. A student who is not will find the decimal point is the least of the difficulties, so check that first with 3-digit by 2-digit multiplication if needed.
Fifth graders learn this skill, and it becomes everyday arithmetic as soon as money, measurement and unit prices appear.
What the problems look like
Each problem is on a single line, such as 3.46 × 4 = ___, and three go across the page. The decimal factor is below 21, so some are less than 1, such as 0.37, and some are in the teens, such as 17.08. The whole-number factor ranges from 2 to 12. There is no stacked layout or work space here, so students will need scratch paper or the margins for the digit-by-digit multiplication.
Settings
- Skill is set to Multiply a decimal by a whole number. The generator also has Multiply decimals (two decimal factors), Add decimals, Subtract decimals, Divide a decimal by a whole number, All four operations and Order decimals.
- Decimal places runs from 1 to 3. One place is the best start, since tenths are easy to picture. Two places match money. Three places give the most room for placement errors.
- Number of problems has a range of 8 to 30, with a default of 20.
The sheet's instruction line explains the method in one sentence: multiply as if there were no decimal point, then place the point so the answer has as many decimal places as the decimal factor.
Worked example: 3.46 × 4
- Ignore the decimal point and multiply 346 × 4. 4 × 6 = 24: write 4, carry 2. 4 × 4 = 16, plus 2 is 18: write 8, carry 1. 4 × 3 = 12, plus 1 is 13. The whole-number product is 1,384.
- Count the decimal places in the decimal factor. 3.46 has two.
- Put the decimal point two places from the right in 1,384. That gives 13.84.
- Estimate to check. 3.46 is close to 3.5, and 3.5 × 4 is 14. The answer, 13.84, is close to 14, so the point is in the right place.
The estimate is the most valuable habit here. A point misplaced by one position gives 138.4 or 1.384, and neither comes anywhere near 14.
Reading the key
The key shows the product without trailing zeros, so a result like 8.60 is printed as 8.6. If a student writes 8.60, the value is the same and counts as correct.
- A product one place off. The student counted from the left instead of the right, or counted the whole-number factor's digits as decimal places.
- A wrong digit with the point right. The error is in the multiplication itself, often in a carried digit. Redo the whole-number product alone.
- Dropped zero. For 0.35 × 4 = 1.40, the student may write 1.4, which is fine, or 14.0, which is not. Estimate again to check.
- Dropping the carry from the tenths. This moves digits into the wrong place values.
Practice goes well together with decimal word problems, where price times quantity uses this exact skill.