8 ones plus 8 ones equal 16 ones. 16 is 1 ten and 6 ones. Record the 6 ones in the ones column between the equals sign. Because we have more tens, we record the 1 ten in the tens column above the equals sign. 6 tens plus 5 tens plus 1 ten equals 12 tens. 12 tens is 1 hundred and 2 tens. Record the 2 tens in the tens column between the equals sign. Because we don’t have more hundreds, we record the 1 hundred in the hundreds column between the equals sign

2 ones plus 9 ones equal 11 ones. 11 is 1 ten and 1 one. Record the 1 one in the ones column between the equals sign. Because we have more tens, we record the 1 ten in the tens column above the equals sign. 8 tens plus 8 tens plus 1 ten equals 17 tens. 17 tens is 1 hundred and 7 tens. Record the 7 tens in the tens column between the equals sign. Because we have more hundreds, we record the 1 hundred in the hundreds column above the equals sign

2 ones plus 9 ones equal 11 ones. 11 is 1 ten and 1 one. Record the 1 one in the ones column between the equals sign. Because we have more tens, we record the 1 ten in the tens column above the equals sign. 8 tens plus 8 tens plus 1 ten equals 17 tens. 17 tens is 1 hundred and 7 tens. Record the 7 tens in the tens column between the equals sign. Because we have more hundreds, we record the 1 hundred in the hundreds column above the equals sign. 6 hundreds plus 5 hundreds plus 1 hundred is 12 hundreds. 12 hundred is 1 thousand and 2 hundreds. Because we have no more thousands, we can record the 1 thousand and 2 hundreds in the thousands and hundreds columns between the equals sign

= = = = 1271

I don’t have enough ones to subtract 8 ones from 7 ones. So I can add ten to both numbers without changing the difference between them. I’ll add 10 ones as 10 ones to the top number. And I’ll add 10 ones as 1 ten to the bottom number. 17 ones minus 8 ones equals 9 ones. We’ll record the 9 ones in the ones column between the equals sign

I don’t have enough ones to subtract 8 ones from 7 ones. So I can add ten to both numbers without changing the difference between them. I’ll add 10 ones as 10 ones to the top number. And I’ll add 10 ones as 1 ten to the bottom number. 17 ones minus 8 ones equals 9 ones. We’ll record the 9 ones in the ones column between the equals sign. I don’t have enough tens to subtract 6 tens from 2 tens. So I can add 10 tens to both numbers without changing the difference between them. I’ll add 10 tens as 10 tens to the top number. And I’ll add 10 tens as 1 hundred to the bottom number. 12 tens minus 5 tens is 7 tens. We’ll record the 7 tens in the tens column between the equals sign

I don’t have enough ones to subtract 8 ones from 7 ones. So I can add ten to both numbers without changing the difference between them. I’ll add 10 ones as 10 ones to the top number. And I’ll add 10 ones as 1 ten to the bottom number. 17 ones minus 8 ones equals 9 ones. We’ll record the 9 ones in the ones column between the equals sign. I don’t have enough tens to subtract 6 tens from 2 tens. So I can add 10 tens to both numbers without changing the difference between them. I’ll add 10 tens as 10 tens to the top number. And I’ll add 10 tens as 1 hundred to the bottom number. 12 tens minus 6 tens is 6 tens. We’ll record the 6 tens in the tens column between the equals sign. 1 hundred plus 1 hundred equals 2 hundred. We’ll record the 2 hundred in the hundreds column between the equals sign

I don’t have enough ones to subtract 8 ones from 7 ones. So I can change 1 ten into 10 ones. Now I have 1 ten and 17 ones. 17 ones minus 8 ones equals 9 ones. We’ll record the 9 ones in the ones column between the equals sign

I don’t have enough ones to subtract 8 ones from 7 ones. So I can change 1 ten into 10 ones. Now I have 1 ten and 17 ones. 17 ones minus 8 ones equals 9 ones. We’ll record the 9 ones in the ones column between the equals sign. I don’t have enough tens to subtract 5 tens from 1 ten. So I can change 1 hundred into 10 tens. Now I have zero hundreds and 11 tens. 11 tens minus 5 tens equals 6 tens

= = = = =

I don’t have enough ones to subtract 8 ones from 7 ones. So I change one ten into 10 ones and now I only have one ten in the tens column. I can subtract 8 ones from 17 ones and put the answer between the equals sign

I don’t have enough tens to subtract 5 tens from one ten. I can change one hundred into ten tens. Now I have 11 tens and zero hundreds. I can subtract 5 ones from 11 ones and get six ones. This procedure tells us to put the answer between the equals sign

1.Select cards to make numbers you are ready to add or subtract. 2.Add or subtract the numbers, explain why your strategy is efficient. 3.Add or subtract using a calculator. Reflection: How do algorithms for addition and subtraction use place value? Investigation: Problem Solving What might the missing numbers be? Find a few: Problem Solving What might the missing numbers be? Find a few: Problem Solving What might the missing numbers be? Find a few :