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.