Question

The average of 25 results is 18. The average of first 12 of those is 14 and the average of last 12 is 17. What is the 13th result?
A.74
B.75
C.69
D.78

Answer 1

Answer:

Step-by-step explanation:

Answer 2

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$average \: = \frac{sum \: of \: numbers}{total \: numbers}$ Sum of 25 numbers = Average x Total numbers
= 25 x 18
= 450
Sum of first 12 numbers = 14 x 12
= 168

Sum of last 12 numbers = 17 x 12
= 204

Now The 13th number is = Sum of 25 numbers - Sum of first 12 numbers - Sum of last 12 numbers
$= 450 - 168 - 204 \\ = 450 - 372 \\ = 78$
So The 13th number is 78
Option D. 78 is your answer

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