A missing addend is the number that is added to a given number in order to get another given number or sum. In the figure below, the given number is 9 and whatever must be added to 9 to get 12 is what we call missing addend.
In the figure above, the missing addend is 3 since 9 + 3 = 12.
Example #1
Suppose you saved 250 dollars to buy a new phone. The new phone costs 600 dollars. How much more money do you need to save to buy the new phone?
Use □ to represent the missing addend.
250 + □ = 600
Since 250 + 350 = 600, the missing addend is 350.
You need 350 dollars more to buy the new phone.
Example #2
A number added to five is -1. What is the number?
Use □ to represent the missing addend.
5 + □ = -1
Since 5 + -6 = -1, the missing addend is -6