Multiplying decimals

About this lesson

Grade 6 › Arithmetic in base ten

To save a PDF, choose “Save as PDF” in the print dialog.

Multiplying decimals

Warm-up

Three quick questions from earlier lessons.

Discover

0.3×0.20.3 \times 0.2: three tenths of two tenths. Which is it?

  1. 0.060.06
  2. 0.60.6

Key idea

Multiply as whole numbers, then count decimal places.

To multiply decimals, multiply as if they were whole numbers. The product has as many decimal places as the factors together (tenths × tenths = hundredths). Estimate to check.

Worked example

1.5×2.41.5 \times 2.4.

15×24=36015 \times 24 = 360
Whole numbers.
3.60=3.63.60 = 3.6
1 + 1 places.

Your turn, guided

Your turn: 0.4×0.70.4 \times 0.7.

0.280.28
28 hundredths.

Practice ★

  1. Compute 6.9×56.9 \times 5.
  2. Compute 9.7×39.7 \times 3.
  1. Compute 0.6×0.60.6 \times 0.6.

Watch out!

Practice ★★

  1. Compute 9.9×1.69.9 \times 1.6.
  2. Compute 4.8×3.54.8 \times 3.5.
  1. Boss problem. Markers cost 1.1 dollars each. You buy 3 markers and pay with a 20-dollar bill.

Exit ticket

Three questions to check you have got it.

  1. Compute 6.9×56.9 \times 5.
  2. Compute 9.7×39.7 \times 3.
  3. Compute 9.6×89.6 \times 8.

Summary card

Multiplying decimals

Multiply, then count the decimal places.

Watch out: estimate to place the point.

End of the lesson

Next lesson: Dividing decimals Back to the chapter

Answers: Multiplying decimals

A

  1. 692\frac{69}{2}
  2. 29110\frac{291}{10}

B

  1. 925\frac{9}{25}

C

  1. 39625\frac{396}{25}
  2. 845\frac{84}{5}

D

  1. 33

E

  1. 692\frac{69}{2}
  2. 29110\frac{291}{10}
  3. 3845\frac{384}{5}

CC BY-SA 4.0