Question

Average of 15 numbers is 7. out of them the average of first 8 numbers is 6.5 and the average of last eight numbers is 9.5. the middle number is

Answer 1

Answer :

Average of 15 numbers = 7
So total sum of all 15 numbers = 15×7 = 105.

Now,average of first 8 numbers = 6.5
It means total sum of first numbers = 8×6.5 = 52

So it means total sum of remaining 7 numbers = 105 - 52 = 53

Now,according to the question,
Average of last 8 numbers = 9.5

So total sum of last 8 numbers = 9.5×8 = 76
But sum of last 7 numbers = 53,
So the middle number = 76 - 53

●=> Middle number = 23


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