Lesson 6: Multiply Decimals6.NOS.3

I can…

I can multiply decimals and place the decimal point correctly in the product.

Key words

• Product — The answer when you multiply.
• Decimal point — The dot that splits the whole number from the part after it.
• Estimate — A close answer you get by rounding first.
• Place value — What a digit is worth based on where it sits in a number.
• Decimal places — How many digits come after the decimal point.

Steps

1. I want 4.5 × 12.60, the cost of 4.5 meters at $12.60 each.
2. First I multiply without points, like whole numbers: 45 × 1260 = 56,700.
3. Now I count decimal places: 4.5 has 1, and 12.60 has 2, so 1 + 2 = 3 decimal places.
4. I put the point 3 places from the right in 56,700: that gives 56.700, or $56.70.
5. I check with an estimate: 5 × $13 = $65, and $56.70 is close, so my answer is reasonable.

Try it

What is 4.6 × 2.3?

Check your answer

10.58

46 × 23 = 1,058. There are 2 total decimal places (1 + 1), so the answer is 10.58.

Sentence starter

I know ___ because ___.

Goal: I can explain my work using the words product, decimal point, estimate, and decimal places.