Question

There are four numbers average of the first three is 17 and of the last three is 20. if he last number is 21, find the first

Answer 1

Answer :

The average of first three numbers = 17

So total sum of first three numbers = 51

The average of last three numbers = 20

So total sum of last three numbers = 60

Since the last number = 21,

=> Sum of 2nd and 3rd number = 60 - 21

=> Sum of 2nd and 3rd number = 39

Lets come back to the sum of first three numbers.

Sum of first three numbers = First number + (Sum of 2nd and third number)

=> 51 = First number + 39

=> First number = 51 - 39

●=> First number = 12


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