GMAT: Questions

The formula for average, or arithmetic mean, is:

Average

=

Sum of terms   Number of terms

We know that the average is 84, that there are 5 terms, and that four of the terms are 73, 81, 83, and 96. We need to know what the fifth term, the x equals. So let's plug appropriately into the average formula. We can simplify this by adding up the numbers in the numerator, which gives us:

Subtract 333 on both sides and we have that x = 87, which is choice (D).

84

=

73  +  81  +  83  +  96  +  x 5

We can simplify this by adding up the numbers in the numerator, which gives us:

84

=

333  +  x 5

To solve for

x,

we multiply by 5 on both sides, which gives us

420

=

333

+

x.

Subtract 333 on both sides and we have that x = 87, which is choice (D).