Grade 1 Math Missing Number in Addition
Missing Number In Addition
What is missing
number in Addition?
When a number
called addend in an addition sentence is absent, then it’s called the missing
number in Addition.
Parts of Addition Sentence:
1^{st} Addend + 2^{nd} Addend = Sum [5 + 3 = 8].
How to find the Missing
number in Addition?
We can find out the
missing number in addition as per the process of subtraction.
When the missing
number is 1^{st} Addend:
In this case, we
shall subtract the 2^{nd} addend from the sum. And the subtracted result
will be equal to the 1^{st} addend or the missing number.
Example:
?

+

2

=

6

Addend

+

Addend

=

Sum

Here,
Missing Number = 1^{st} Addend = ?
And 1^{st}
Addend = Sum – 2^{nd} Addend = 6 – 2 = 4.
So, the Missing
number = 9.
When the missing
number is 2^{nd} Addend:
In this case, we
shall subtract the 1^{st} addend from the sum. And the subtracted result
will be equal to the 2^{nd} addend or the missing number.
Example:
4

+

?

=

6

Addend

+

Addend

=

Sum

Here,
Missing Number = 2^{nd} Addend = ?
And 2^{nd}
Addend = Sum – 1^{st} Addend = 6 – 4 = 2.
So, the Missing
number = 2.
1. Find the missing number in the following sentences (a to f).
(a) 5 + ? = 7.
Solution:
Here, 7 – 5 = 2.
[Because, 2^{nd} Addend = Sum – 1^{st} Addend]
So, Missing number
= 2.
and 5 + 2 = 7.
(b) 8 + ? = 15.
Solution:
Here, 15 – 8 = 7.
[Because, 2^{nd} Addend = Sum – 1^{st} Addend]
So, Missing number
= 7.
and 8 + 7 = 15.
(c) 90 + ? = 100.
Solution:
100 – 90 = 10.
[Because, 2^{nd} Addend = Sum – 1^{st} Addend]
So, Missing number
= 10.
and 90 + 10 = 100.
(d) ? + 1 = 1.
Solution:
Here, 1  1 = 0.
[Because, 1^{st} Addend = Sum – 2^{nd} Addend]
So, Missing number
= 0.
and 0 + 1 = 1.
(e) ? + 50 = 60.
Solution:
Here, 60 – 50 = 10.
[Because, Minuend = Subtrahend + Difference]
So, Missing number
= 10.
and 10 + 50 = 60.
(f) ? + 13 = 17.
Solution:
Here, 17  13 = 4
[Because, 1^{st} Addend = Sum – 2^{nd} Addend]
So, Missing number
= 4.
and 4 + 13 = 17.