SAT Subject Test Mathematics Level 2

AVERAGES

Another classic situation with a standard approach is an averages question like Example 6.

Example 6

Call the average monthly sales for February through December 2x. Then the monthly sales for
January were 3x. Total annual sales equal the sum of monthly sales for January and each of the 11
months from February through December, inclusive. In other words, total annual sales equal 3 x +
2 x(11) = 25x. And of that 25x, what portion is January? Again—3x. So January’s total sales as a
fraction of total annual sales is .

The answer is (C).

USE THE SUM

The key to  many    averages    questions   is  to  use this    variant of  the Average formula:

Sum of  the terms   =   (Average)   ×   (Number of  terms)

Last    year    a   manufacturer    had a   sales   total   for January that    was 50  percent greater than    the

average (arithmetic mean)   of  the monthly sales   totals  for February    through December.   The sales

total   for January was what    fraction    of  the sales   total   for the year?

1.

(A)

(B)

(C)

(D)

(E)