Subtraction

1
Subtraction

• Subtraction is a process of taking away
• Look at the examples
• 2 1 1

2 Take away 1 Leaves 1
2
4 -2 2
4 take away 2 leaves 2
3
7 4 3
7 take away 4 leaves 3
4

• The Sign indicates subtraction. It is read as
  minus sign. We read 5 3 2 as five minus three
  is equal to two. 5 3 2 is called a
  subtraction fact.
• In 5 3 2, 2 is called the difference of 5 and
  3.

5
Fill in the boxes
6 2 3 1
6
Using counters, find the difference
7 - 3 8 -3 5 - 1
5 -4 8 - 6 9 - 3
7
Properties of Subtraction
4 take away 0 leaves 4
3 take away 0 leaves 3
8

• What do we observe?
• We see that when 0 is subtracted from a number,
  the number remains the same.
• Again observe the following

3 3 0 1 1 0
9
Fill in the boxes
1. 4 0 6. 5 - 0
2. 12 0 7. 15 - 15
3. 3 - 3 8. - 2 0
4. 9 - 9 9. 9 0
5. - 0 7 10. - 11 0
10
More about subtraction
4 tens 2 tens 2 tens 40 - 20 20 7 tens 3 tens 4 tens 70 30 40
11

• What do we observe ?
• We see that when we subtract 10, 20, 30 etc, from
  40,50, 60 e.t.c, we subtract tens only. Then we
  put a zero to the right of the difference
  obtained above.
• For example, 60 20
• There are 6 tens. 2 tens are taken away.
• 6 2 4
• So we have 60 20 40.

12
Fill in the boxes
40 10 2. 50 30 3. 70 20 4. 60 30 5. 90 40 6. 30 20 7. 60 50 8. 80 10 9. 70 60 10. 90 30 11. 70 30 12. 50 20
13
More about subtraction Observe the following
4 tens 2 tens 2 tens 40 20 20 7 tens 3 tens 4 tens 70 30 40
14
What do we observe?

• We see that when we subtract 10,20,30 e.t.c from
  40, 50,60 e.t.c, we subtract tens only. Then we
  put a zero to the right of the difference
  obtained above.
• For example, 60 20
• There are 6 tens. 2 tens are taken away.
• 6 2 4
• So, we have 60 20 40.

15
Fill in the boxes
40 10 50 30 70 20 60 30 5. 90 40 6. 30 20 7. 60 - 50 8.80 10 9. 70 16 10. 90 30 11.70 3- 12.50 20
16
Observe the following
54 30 24 42 30 12
17
What we observe?

• We see that when we subtract 10 or 20 or 30 etc.,
  from a number we take away tens only. There is no
  change in ones.
• For example, 76 20
• There are 7 tens. 2 tens are taken away.
• Thus, 7 2 5 tens are left over and there is no
  change in ones. So, we have 76 20 56.

18
Fill in the boxes
51 20 66-30 87 40 93 50 5. 63 60 6. 89 40 7. 71 50 8. 82 60 9. 84 30 10. 63 20 11. 74 10 12. 57 40
19
Subtraction without Regrouping ( or without
Borrowing)

• Subtract 23 from 44
• Expanded form 44 4 tens 4
  ones
• - 23
  2 tens 3 ones
• 
  2 tens 1 one
• so, 44 23 2
  tens 1 one
• 
  21

20
Short Form
T O 4 4 - 23 T O 44 - 23 1 T O 4 4 - 23 2 1

• Step 1. Arrange the given numbers in
  columns.Write the greater number above the
  smaller number.
• Step 2. Subtract the digits in ones column.
• Step 3. Subtract the digits in tens column.

21
Subtract
93 - 52 45 - 24 99 - 87 45 - 34
22
Regrouping of Numbers from Tens to ones
1 ten 3 ones 13 ones
23
2 tens 4 ones 1 tens 14 ones
24

• In the same way, we have
• 1. 6 tens 5 ones 5 tens 15 ones
• 2. 4 tens 9 ones 3 tens 19 ones
• 3. 8 tens 0 ones 7 tens 10 ones

25
Fill in the boxes

• 1. 2 tens 4 ones ten 14 ones
• 2. 3 tens 2 ones 2 tens ones
• 3. 8 tens 3 ones tens 13 ones
• 4. 7 tens 4 ones 6 tens ones
• 5. 9 tens 0 ones 8 tens ones
• 6. 5 tens 6 ones tens 16 ones

26
Subtraction with Regrouping (or with Borrowing)

• Subtract 16 from 34.
• Write the numbers under T and O columns.
• Leave a gap just below T and O.
• T O Method
• 2 14 step 1 4 ones 6 ones is not
  possible.
• 3 4 Regroup 3 tens as 2
  tens 1 ten 2 tens
• - 1 6 10 ones.
• 1 8 Now 10 ones 4 ones
  14 ones.
• 14 ones 6 ones 8
  ones.
• Write 8 in the ones
  place of the answer.
• Step 2 2 tens 1 ten 1 ten.

27
Subtract the following
T O 3 5 - 1 8 T O 3 6 - 1 7 T O 3 7 - 1 9 T O 4 3 - 1 5
T O 8 4 - 2 5 T O 8 5 - 3 7 T O 9 4 - 4 3 T O 7 5 - 2 6

28
Addition and Subtraction

• Find 10 5 3
• Step 1 First add 10 and 5
• 1 0 step 2
  subtract 3 from 15
• 5 1 5
  
• 1 5 10 - 3
  
• or 5 12
• 15

29
Find 25 -7 14

• step 1
• 1 15
• 2 5
• - 7 1
• 1 8 18
• 14
• 32 Hence, 25
  7 14 32