Lesson 2.122.12 Small Group · Group 1
Start hereWords, worked example, and sentence starters
Learning target With my small group, I can multiply decimals and place the decimal point correctly in the product — one step at a time, with support.
Start hereWords for this lesson
Read each word before you begin. Say it out loud.
| Word | What it means | Example |
|---|---|---|
| ProductSpanish: Producto | The answer when you multiply. | 4 × 7 = 28, so the product is 28 |
| Decimal pointSpanish: Punto decimal | The dot that splits the whole number from the part after it. | In 3.25, the decimal point separates 3 (ones) from 25 (tenths and hundredths) |
| EstimateSpanish: Estimar | A close answer you get by rounding first. | 3.7 × 4.2: round to 4 × 4 = 16, so the exact answer should be near 16 |
| Place valueSpanish: Valor posicional | What a digit is worth based on where it sits in a number. | In 0.36: the 3 is in the tenths place (0.3) and the 6 is in the hundredths place (0.06) |
| Decimal placesSpanish: Cifras decimales | How many digits come after the decimal point. | 3.4 (1 place) × 2.6 (1 place) = 8.84 (2 places total) |
How it worksWorked example
These numbers are not on your problems. The steps are. Follow them with your own numbers.
One meter of cloth costs $12.60. What is the cost of 4.5 meters? Find 4.5 × 12.60.
- Write one meter in the table: 1 m → $12.60
- Find the scale factor: 4.5 ÷ 1 = 4.5
- Multiply as if there were no decimal points: 45 × 1260 = 56700
- Put the point 3 places from the right: 1 + 2 = 3; 56700 → 56.700
- Check with an estimate: 5 × 13 = 65
- 4.5 meters cost $56.70.
Now you trySame steps, your turn
The steps are the same as the worked example. The numbers are yours. Do the work.
Multiply 0.4 × 0.7.
Say it and write itSentence starters
Finish each sentence out loud with a partner. Then use them in your writing.
- I estimated x by rounding to x = , which told me the product is than 20.
Word bank ProductDecimal pointEstimatePlace valueDecimal placesestimaterounddecimal placesproductmultiplyreasonable
Watch outA common mistake
A common mistake in Multiply Decimals is counting decimal places from only one factor instead of adding the decimal places from BOTH factors. For example, in 0.4 × 0.06, a student multiplies 4 × 6 = 24, then places the decimal point using just one factor's place count (1 place), writing 0.24 instead of the correct answer: 0.4 has 1 decimal place and 0.06 has 2 decimal places, for a total of 3, so 24 becomes 0.024. Before you submit, count the decimal places in EACH factor separately and add them together — that total is how many decimal places belong in your final answer.
Lesson 2.122.12 Small Group · Group 1
Group 1Supported practice
Learning target With my small group, I can multiply decimals and place the decimal point correctly in the product — one step at a time, with support.
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1Complete each step, then write the final answer.
Find 0.3 × 0.4.
Show your workHint Multiply 3 × 4. Then count the decimal places in both factors.
Final answer: -
2Complete each step, then write the final answer.
Find 6.2 × 3.4.
Show your workHint Multiply 62 × 34 first. Each factor has 1 decimal place.
Final answer:
-
3Complete each step, then write the final answer.
6 tenths of 8 tenths. Multiply 0.6 × 0.8.
- 1Multiply like whole numbers. What is 6 × 8?
- 2How many decimal places are in 0.6 and 0.8 together?
- 3Put the point 2 places from the right in 48. What do you get?
Final answer: -
4Complete each step, then write the final answer.
Add the four parts to check the product. Multiply 2.3 × 1.5.
- 1Multiply like whole numbers. What is 23 × 15?
- 2Count the decimal places in both factors.
- 3Put the point 2 places from the right. What is the product?
Final answer: -
5Complete each step, then write the final answer.
Apples cost $1.15 per pound. How much do 3.2 pounds of apples cost?
Show your workHint Multiply 115 × 32. Then count the decimal places: 2 in $1.15 and 1 in 3.2.
Final answer: -
6Complete each step, then write the final answer.
Jay says 0.2 × 0.3 is 0.6. Is he right? What is the product?
Show your workHint Count the decimal places in both factors. How many places must the product have?
Final answer:
Explain your thinkingJay got 0.6. How does counting decimal places help you fix his answer?
Sentence starter The factors have ___ decimal places in all, so ___. · Jay's answer has only ___ decimal place, but it needs ___.