You can break apart a number using place value to help you add. 24 is 2 tens and 4 ones. 24 = 20 + 4. When you break apart two numbers, you can add the tens then add the ones.

**To better understand Adding & Subtracting within 100…**

## LET’S BREAK IT DOWN!

### Place-Value Blocks

Place value is the value of a digit based on its position in a number. The 4 in 49 represents 4 tens. The 9 represents 9 ones. 49 = 40 + 9. You can use place-value blocks to show 4 tens and 9 ones. Erika adds 1 more ones block to the pile. Now there are 10 ones. 10 ones is the same as 1 ten. Now there are 5 tens. 5 tens = 50. Try this one yourself: **How can you represent 68 with place-value blocks?**

### Candy Apples

Erika has dipped 24 candy apples. Dane has dipped 35. How many candy apples have they dipped in all? Find 24 + 35. 24 is 2 tens and 4 ones. 35 is 3 tens and 5 ones. Add the ones and add the tens. 20 + 30 = 50. 4 + 5 = 9. The total is 50 + 9 = 59. Try this one yourself: **Erika has dipped 33 candy apples. Dane has dipped 41 candy apples. How many have they dipped in all?**

### Flowers

There are 58 blue flowers and 37 red flowers. How many flowers are there in all? Find 58 + 37. 58 is 5 tens and 8 ones. 37 is 3 tens and 7 ones. 50 + 30 = 80. 8 + 7 = 15. Altogether there are 8 tens and 15 ones. Regroup 10 ones as 1 ten. That makes 9 tens and 5 ones, or 95 in all. Try this one yourself: **There are 48 yellow flowers and 36 purple flowers. How many flowers are there in all?**

### Plastic Bricks

Erika has 65 blocks. She gives Dane 41 blocks. How many blocks does Erika have left? Find 65 – 41. 65 is 6 tens and 5 ones. 41 is 4 tens and 1 one. Subtract by place value. 60 – 40 = 20. 5 – 1 = 4. The answer is 2 tens and 4 ones, or 24. Erika has 24 bricks left. Try this one yourself: **Erika has 87 blocks. She gives Dane 35 blocks. How many blocks does Erika have left?**

### Ant Farm

Dane has 71 ants in his ant farm. He gives Erika 38 ants. How many ants does Dane have left? Find 71 – 38. 71 is the same as 70 + 1. 38 is the same as 30 + 8. Try to subtract the ones. You can't take away 8 ones from 1 one. Regroup 1 ten in 71 as 10 ones. So 70 = 60 + 11. Subtract the ones. 11 – 8 = 3. Subtract the tens. 60 – 30 = 30. The difference is 30 + 3 = 33. Dane has 33 ants left. Try this one yourself: **Dane has 82 worms. He gives Erika 49 worms. How many worms does Dane have left?**

## ADD & SUBTRACT WITHIN 100 VOCABULARY

## ADD & SUBTRACT WITHIN 100 DISCUSSION QUESTIONS

### How can place value help you to add numbers?

### When do you need to regroup when adding 2-digit numbers? How do you regroup?

### Find 26 + 12. Do you need to regroup?

### When do you need to regroup when subtracting 2-digit numbers? How do you regroup?

### Find 34 – 29. Do you need to regroup?

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