Multiply Whole Numbers by Decimals Mentally

Start with the mental math sheet so students see how each zero and each decimal place moves the point. Then use the written sheet and finish with missing factors.

Multiply 24 whole numbers by decimals mentally, like 0.009 × 400 and 90 × 0.05. Multiply the nonzero digits. Then move the decimal point one place left for each decimal place, and one place right for each zero in the whole number. The directions on the page read: Multiply in your head. Write each product. An answer key is included.

Yes, both. We made it for 6th Grade decimal multiplication, and the page works the same whether it lands on a kitchen table or a center rotation. At home, most families go through it together and talk the answers out loud, and that talking is where most of the learning happens with whole numbers times decimals. In class it runs well as independent work while you pull a small group. Print one copy or thirty, whichever the day needs.

Multiply as if there were no decimal point, then give the product as many decimal places as the decimal factor. On Multiply 1-Digit Numbers by Longer Decimals, 4 × 0.94 is 4 × 94 = 376, so the product is 3.76.

Multiply the nonzero digits, move the point left for each decimal place and right for each zero in the whole number. On Multiply Whole Numbers by Decimals Mentally, 0.009 × 400 is 9 × 4 = 36, moved 3 places left and 2 places right, which gives 3.6.

Divide the product by the factor you know. On Missing Factors With Decimals Times Whole Numbers, 8 times a number equals 5.6, so the missing factor is 5.6 ÷ 8 = 0.7.