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Solve Problems with Decimals (Using Models)
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What you will learn from this videoWhat you will learn
- We’ll add, subtract, multiply and divide decimals using models.
- We will also learn how to use estimation to decide if our answer is reasonable.
- And that this knowledge can help us feed our pets, go hiking and even grow crystals!
- Discussion Questions
Before Video
Give the value of each digit in 5.39.ANSWER5 wholes, 3 tenths, and 9 hundredths
Every 10 hundredths can be regrouped as 1 tenth. So, 56 hundredths is 5 tenths and 6 hundredths.
Every 10 tenths can be regrouped as 1 whole. So, 48 tenths is 4 wholes and 8 tenths.
If I divide 63 wholes equally among 9 groups, each group has 7 wholes. 63 ÷ 9 = 7.
I can round 58 to 60, and 32 to 30. 60 × 30 is 1,800, which is close to 1,856. This is how I know my answer makes sense.
After Video
If you are calculating 3.64 – 2.14, which number should you represent using the fraction square model? What is the second step? ANSWERThe greater number, 3.64. Then, take away blocks that represent 2.14 in total.
I don’t have enough tenths to subtract 8 tenths, so I need to regroup 1 of the wholes as 10 tenths. Then, I have 2 wholes and 14 tenths. Now I can subtract 8 tenths from 14 tenths. The answer is what remains, 2 wholes and 6 tenths, or 2.6.
1.4 means 1 whole and 4 tenths. I need to multiply each number by 6, which is the same as skip counting sixes. 6 × 1 = 6. 6 × 4 tenths = 24 tenths. 24 tenths is the same as 2 wholes and 4 tenths, so altogether I have 8 wholes and 4 tenths, or 8.4.
No, Mimi needs to do some regrouping, starting with the smallest place, the hundredths place. 28 hundredths can be regrouped as 2 tenths and 8 hundredths. So, now there are 8 wholes, 12 + 2 = 14 tenths, and 8 hundredths. Next, regroup some of the tenths. 10 tenths can be regrouped as 1 whole, so the final answer is 9 wholes, 4 tenths, and 8 hundredths, or 9.48.
I can round 3.8 to 4 and 5.1 to 5. Multiply: 4 × 5 = 20. 20 is close to 19.38, so the answer makes sense.
- Vocabulary
- Place value DEFINE
Tells us the value of a digit based on its position in a number.
- Decimals DEFINE
Numbers that allow us to show parts of a whole.
- Ones place DEFINE
Shows the number of wholes.
- Tenths place DEFINE
Shows the number of parts out of 10.
- Hundredths place DEFINE
To the right of the tenths place, and shows us the number of parts out of 100.
- Models DEFINE
Visual tools that help us to represent numbers.
- Regroup DEFINE
When we have 10 of one place value, we can regroup to create 1 of the place value on its left.
- Place value DEFINE
- Reading Material
- Practice Word Problems
- Practice Number Problems
- Lesson Plan
- Teacher Guide
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