2. 68 + 58 = 126 Addition and Subtraction 17 68 108 68 + 58 = 2 + 6 40 +10 + 68 126 120 118108 98 88 78 + 40 118 + 10 40 +10 + 40 + 10 + 2 + 6

3. Addition and Subtraction 17 68 + 58 = 68 + 60 = 128 128 – 2 = 126

4. Addition and Subtraction 17 126 76 106 126 - 58 = 20+30 + 6 + 2 126 - 58 = 68 50 + 8 -20 -30 126 76 106

5. Addition and Subtraction 17 126 -58 = 126 – 60 = 66 66 + 2 = 68

6. Addition and Subtraction 17 1.Select cards to make two-digit numbers where the tens add to more than 100 and the ones add to more than 10. 2.Add the numbers using place value, recording on a number line. 3.If one of the numbers is close to a place value, add using compensation. 4.Select cards to make a two-digit number to subtract from a number in the 100s where the tens subtract into the hundred below, and the ones subtract into the tens below. 5.Subtract the numbers using place value, recording on a number line. 6.If the number you are subtracting is close to a place value, subtract using compensation. Reflection: How can we add and subtract two-digit numbers? Investigation: Problem Solving Lola collected 84 cans. Jill collected 98 cans. How many cans did Lola and Jill collect altogether? Problem Solving Altogether Lola and Jill collected 117 cans. Jill collected 38 cans. How many cans did Lola collect?

7. Addition and Subtraction 17

8. Investigation: 1.Sit with a friend. 2.Each of you selects 4 cards to make 2 two-digit numbers where the tens digits add to more than 100 and the ones digits add to more than 10. 3.Each of you add your numbers using place value, recording on a number line. 4.Explain your strategy to a friend. 5.The child with the highest (or lowest) total wins. Reflection: How can we add two-digit numbers?

9. Addition and Subtraction 17 Investigation: 1.Sit with a friend. 2.Select cards to make a two-digit number to subtract from a number in the 100s where the tens subtract into the hundred below, and the ones subtract into the tens below. 3.Each of you subtract the numbers using place value, recording on a number line. 4.Explain your strategy to a friend. 5.The child with the highest (or lowest) difference wins. Reflection: How can we subtract two-digit numbers?

10. Addition and Subtraction 17 Investigation: 1.Sit with a friend. 2.Use a calculator to add two-digit numbers where the tens digits add to more than 100 and the ones digits add to more than 10. 3.Check using place value. Reflection: How can we add tens numbers?

11. Addition and Subtraction 17 Investigation: 1.Sit with a friend. 2.Use a calculator to subtract a two-digit number from a number in the 100s where the tens subtract into the hundred below, and the ones subtract into the tens below. 3.Check using place value. Reflection: How can we subtract two-digit numbers?

12. Addition and Subtraction 17 Investigation: 1.Sit with a friend. 2.Flip 2 cards to make a two-digit target number, for example, 28 3.Flip 2 more cards to make a two-digit starting number, for example, 93. 4.Take turns to flip a card and decide whether to add or subtract the number as a one or a ten, for example, flip 6 and decide to subtract it as 6 tens. 5.Keep a running total. 6.When the total is within one digit of the target number, you may ‘wish’ for the digit, for example,  if the total is 22, you may ‘wish’ for a 6 and add it as 6 ones  if the total is 38, you may ‘wish’ for a 1 and subtract it as 1 ten. 7.Keep a record of the number of turns it took you to reach the target number. 8.Play again attempting to reach the next target number is fewer turns. 9.(This game is based on WISHBALL TENS. Other levels of Wishball are also available on the Internet and as Apps.)WISHBALL TENS Reflection: How can we add and subtract to two-digit numbers?