Question

The average of 11 numbers is 68. If the average of the first five is 63 and the average of the last five is 72, find the 6th number.

• A. 73
• B. 74
• C. 75
• D. 76

Answer 1

Answer:

A. 73

Average of 11 numbers = 68

So, total of all 11 numbers:

$11 \times 68 = 748$

Average of first 5 numbers = 63

So, sum of first 5 numbers:

$5 \times 63 = 315$

Average of last 5 numbers = 72

So, sum of last 5 numbers:

$5 \times 72 = 360$

Let the 6th number be (x).

Then:

$315 + x + 360 = 748$
$675 + x = 748$
$x = 748 - 675 = 73$

Therefore, the 6th number is:

$\boxed{73}$