There, we covered the use of Subtraction
Table and a number of examples on
Subtracting two digit numbers.
That knowledge is a prerequisite here.
Here, we deal with three digit numbers.
Subtraction of three digit numbers
We have already seen in decimal number system
that the successor to 99 is 100.
or the predecessor to 100 is 99.
i.e. 100 - 1 = 99.
Let us present this process in the
vertical presentation by using the
borrow method (also called regrouping
method) explained in Subtraction of Two Digit Numbers.
1009010
1
----
99
----
First we have to subtract bottom digit
in the units' place from the upper
digit in the units' place.
i.e. we have to subtract 1 from 0.
But 1 is bigger than 0.
So, we have to borrow one (one10)
from the digit in tens' place i.e. 0.
0 as it is can not give 1. So it borrows
1 (one10) from the 1 in hundreds' place.
Because of this borrowing, 0 in units'
place becomes 10 and 0 in tens' place
with the borrowed 10 becomes 9
and 1 in hundreds' place becomes 0.
Now subtract 1 from 10 which
gives 9 in the units' place.
In Tens' place, we have to descend
the 9 since there is nothing to
subtract in tens' place.
What is left in hundreds' place is
only 0 which can be ignored.
So the answer is 99.
See 0 in the units' place is
sriked off to become 10,
and 0 in the tens' place is
sriked off to become 9,
and 1 in the hundreds' place is
sriked off to become 0.
Thus 100 - 1 = 99. Ans.
We also saw in the decimal number system,
that the three digit numbers
range from 100 to 999.
Knowing these numbers in figures and
in words is a prerequisite here.
In 3 Digit Subtraction, this
borrowing will go one place further.
Solution to Example 1 of 3 Digit Subtraction : The vertical presentation of the problem is shown below.
725
189
-----
-----
First we have to subtract bottom digit in the units' place from the upper digit in the units' place.
i.e. we have to subtract 9 from 5.
But 9 is bigger than 5. So, we have to borrow one (one10) from the digit in tens' place i.e. 2.
Because of this borrowing, 5 in units' place becomes 15 and 2 in tens' place becomes 1.
Now subtract 9 from 15 which gives 6 in the units' place.
Now, we have to subtract bottom digit in the tens' place from the upper digit in the tens' place.
i.e. we have to subtract 8 from 1.
But 8 is bigger than 1. So, we have to borrow one (one10) from the digit in hundreds' place i.e. 7.
Again recall that,
When we borrow 1 from the immediate left digit, that borrowing makes the digit in the right place increase by 10. This is so, because the immediate left place value is 10 times the place value of the right.
Here the borrowing is applied from hundreds' place to the tens' place.
Because of this borrowing, 1 in tens' place becomes 11 and 7 in hundreds' place becomes 6. Now subtract 8 from 11 which gives 3 in the tens' place.
Now subtract 1 from 6 which gives 5 in the hundreds' place.
So the answer is 536.
This process is shown in the vertical presentation below.
76211515
189
----
536
----
See 5 in the units' place is sriked off to become 15,
and 2 in the tens' place is sriked off to become 11.
2 in the tens' place first became 1 by giving 1 to units' place and later became 11 by borrowing 1(one 10) from hundreds' place.
These two steps are not shown seperately.
7 in the hundreds' place is sriked off to become 6.
Thus 725 - 189 = 536. Ans.
Check : You may add 536 and 189 and check whether it is equal to 725 or not.
536
189
11
---
725
---
It is verified to be correct.
Example 2 of 3 Digit Subtraction
Subtract 78 from 362 and then
Subtract 9 from the result.
Solution :
The vertical presentation of
subtracting 78 from 362 is shown below.
362
78
-----
-----
32615212
78
----
284
----
Check :
You may add 284 and 78 and check
whether it is equal to 362 or not.
284
78
11
---
362
---
It is verified to be correct.
Now we have to subtract
9 from the result, 284.
The vertical presentation of
the process is shown below.
284
9
-----
-----
287414
9
----
275
----
Check :
You may add 275 and 9 and check
whether it is equal to 284 or not.
275
9
1
---
284
---
It is verified to be correct.
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Subtract the second number from
the first. Also, check your answer
by doing the appropriate addition.
487, 398
630, 247
234, 97
300, 9
111, 88
934, 745
257, 8
107, 19
633, 155
816, 37
For Answers, see at the end of the page.
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