Step-by-step Maths Level 2: Taking away 10 from a number up to 20

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   13
2. Take away one ten. Take away 10 from the tens.
   13 - 10 = 3
3. Write the answer. The ones stay the same.
   3

Check. Add 10 back: 3 + 10 = 13.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   15
2. Take away one ten. Take away 10 from the tens.
   15 - 10 = 5
3. Write the answer. The ones stay the same.
   5

Check. Add 10 back: 5 + 10 = 15.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   16
2. Take away one ten. Take away 10 from the tens.
   16 - 10 = 6
3. Write the answer. The ones stay the same.
   6

Check. Add 10 back: 6 + 10 = 16.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   19
2. Take away one ten. Take away 10 from the tens.
   19 - 10 = 9
3. Write the answer. The ones stay the same.
   9

Check. Add 10 back: 9 + 10 = 19.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   17
2. Take away one ten. Take away 10 from the tens.
   17 - 10 = 7
3. Write the answer. The ones stay the same.
   7

Check. Add 10 back: 7 + 10 = 17.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   20
2. Take away one ten. Take away 10 from the tens.
   20 - 10 = 10
3. Write the answer. The ones stay the same.
   10

Check. Add 10 back: 10 + 10 = 20.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   12
2. Take away one ten. Take away 10 from the tens.
   12 - 10 = 2
3. Write the answer. The ones stay the same.
   2

Check. Add 10 back: 2 + 10 = 12.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   16
2. Take away one ten. Take away 10 from the tens.
   16 - 10 = 6
3. Write the answer. The ones stay the same.
   6

Check. Add 10 back: 6 + 10 = 16.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   18
2. Take away one ten. Take away 10 from the tens.
   18 - 10 = 8
3. Write the answer. The ones stay the same.
   8

Check. Add 10 back: 8 + 10 = 18.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   14
2. Take away one ten. Take away 10 from the tens.
   14 - 10 = 4
3. Write the answer. The ones stay the same.
   4

Check. Add 10 back: 4 + 10 = 14.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   11
2. Take away one ten. Take away 10 from the tens.
   11 - 10 = 1
3. Write the answer. The ones stay the same.
   1

Check. Add 10 back: 1 + 10 = 11.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   18
2. Take away one ten. Take away 10 from the tens.
   18 - 10 = 8
3. Write the answer. The ones stay the same.
   8

Check. Add 10 back: 8 + 10 = 18.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   12
2. Take away one ten. Take away 10 from the tens.
   12 - 10 = 2
3. Write the answer. The ones stay the same.
   2

Check. Add 10 back: 2 + 10 = 12.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   17
2. Take away one ten. Take away 10 from the tens.
   17 - 10 = 7
3. Write the answer. The ones stay the same.
   7

Check. Add 10 back: 7 + 10 = 17.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   14
2. Take away one ten. Take away 10 from the tens.
   14 - 10 = 4
3. Write the answer. The ones stay the same.
   4

Check. Add 10 back: 4 + 10 = 14.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.

Method. Taking away 10 takes away one ten. Only the tens digit changes.

1. Look at the number. It has one ten and some ones.
   11
2. Take away one ten. Take away 10 from the tens.
   11 - 10 = 1
3. Write the answer. The ones stay the same.
   1

Check. Add 10 back: 1 + 10 = 11.

Watch out. Taking away 10 changes the tens, not the ones: 17 - 10 = 7.