Subtraction is the application of established properties, rules and methods to reduce the sum of numeric quantity. Simple integer subtraction only considers positive whole numbers, but the result can be negative, zero or positive.
1  1 = 0
7  5 = 2
9  1 = 8
6  0 = 6
1  1 = 2
7  5 = 12
9  1 = 10
6  0 = 6
Six apples and six oranges is not a dozen of either apples or oranges. We do not sum or subtract items that are not the same. We could be interested in the total number of apples and oranges if they were combined. Like the same box or bag, to make sure the container is large enough for all items.
2 digit subtraction when one or more numbers is 2 digits.
34
 27
7
Can be written or expressed as: 34  27 = 7
Without subtraction borrowing:
30  20 = 10
04  07 = 3
34  27 = 7
We must work with the 3 value (10  3) to determine the answer.
Without subtraction borrowing:
(30  10)  20 = 20  20 = 0
(10 + 04)  07 = 14  07 = 7
34  27 = 7
When subtracting 7 from 4 (4  7) it results in 3 (as shown above). Recognizing the result is negative we “borrow” 1 from the nearest left column. Each 1 that is borrowed from the nearest left column has a value 10 times greater than the column that is borrowing. The ten is added to 4 resulting in the value of 14, (10 + 4).
49
 7
 83
 41
Can be expressed as: 49  7  83 =  41
40
9
49



0
7
7



80
3
83
=
=
=
40
1
41
Group numbers to be subtracted using parenthesis:
(49  7)  83 = 42  83 = 41
40
2
42



80
3
83
=
=
=
40
1
41
Three digit subtraction  one or more numbers is 3 digits.
125
 362
 839
1,076
Can be expressed as: 125  362  839 = 1,076
Without grouping numbers:
100
20
5
125




300
60
2
362




800
30
9
839
=
=
=
=
1000
70
6
1,076
Group numbers to be subtracted using parenthesis:
(125  362)  839 = 1,076
100
20
5
(125




300
60
2
362)
=
=
=
=
200
40
3
237
(237)  839 = 1,076
200
30
7
237




800
30
90
839
=
=
=
=
1000
60
16
1,076
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