Category : 4th Class
Addition and Subtraction
Synopsis
e.g.,
20165 
+ 
9312 
= 
29477 
Addend 

Addend 

Sum 
Properties of addition:
e.g., 4126+3143 =7269
Also, 3143+4126 =7269
e.g., 6740 + 0 = 6740
In other words, when zero (0) is added to any number, the sum obtained is the number itself.
e.g., 5365 + 2234 = 7599
7599 > 5365 and 7599 > 2234
Addition (Using estimation):
e.g., Add 3451 and 6215.
The addends can be estimated to the nearest 1000 or 100.
(a) Estimating to the nearest 1000:
So, 3000+6000 =9000
Actual sum = 3451 + 6215 = 9666
(b) Estimating to the nearest 100:
3451 rounds to 3500.
9700 is closer to the actual sum i.e., 9666 than 9000.
So, rounding a 4digit addend to the nearest 100 gives a better estimate of the sum.
e.g.,
62135 
 
30014 
= 
32121 
Minuend 

Subtrahend 

Difference 
Properties of subtraction:
(a) While subtracting, the order in which numbers are taken is important.
e.g., 4261  3417 is not the same as 3417  4261.
Note: Only smaller number can be subtracted from the larger ones.
(b) When '0' is subtracted from a number/the difference is the number itself.
(c) On adding the difference and the subtrahend, we get the minuend.
(d) The difference of two numbers is always lesser than the minuend.
(e) When a number is subtracted from itself, the difference is zero.
Subtraction (using estimation):
e.g., Subtract 3451 from 6215.
The subtrahend and the minuend can be estimated to the nearest 1000 or 100.
(a) Estimating to the nearest thousand:
3451 rounds to 3000.
6215 rounds to 6000.
So,
(b) Estimating to the nearest hundred:
3451 rounds to 3500.
6215 rounds to 6200.
So,
Actual difference
2700 is closer to the actual difference i.e., 2764 than 3000.
So, rounding to the nearest hundred gives a better estimate of the difference.
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