Finding a Missing Number when Average and Some Numbers are Given

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1. Finding a Missing Number when Average and Some Numbers are Given

The same average formula is used: 

Average = Total Sum of all Numbers​ / Number of Numbers

From this,

Total Sum = Average × Number of Numbers

Then,

Missing Number = Total Sum − Sum of Given Numbers

Example 1:

The average of 5 numbers is 20.
Out of them, 4 numbers are given: 18, 22, 20, 24.
Find the 5th number.

1^st : Find the total sum

Total Sum = 20×5 = 100

2^nd : Find the sum of the given 4 numbers

18+22+20+24=84

3^rd : Find the missing number

Missing Number = 100−84=16

So, the 5th number = 16