A) 6 n + 18
B) 5 n
C) n + 18
D) n + 6Here’s How to Crack It
Plug in for the value of n. If n = 20, then you can use the Average Pie to find the total of the five numbers
on the list.
As shown on the Average Pie above, the total of the 5 numbers is 100. Now, it’s time for another Average
Pie. For this pie, you know that there are 6 numbers and that their average is 20 + 3 = 23.
Using the Average Pie as shown above, the total of the six numbers is 138. Since the difference in the two
totals was caused by the addition of the sixth number, the sixth number must be 138 – 100 = 38. That’s the
target, so be sure to circle it. Only (C) is 38 when n = 20.
On the SAT, you’ll also need to know three other statistical topics related to averages: median, mode, and
range. These topics have pretty straightforward definitions. One way the SAT will complicate the issue is
by presenting the data in a chart or graph, making it harder to see the numbers you are working with.
What Is a Median?
The median of a list of numbers is the number that is exactly in the middle of the list when the list is
arranged from smallest to largest, as on a number line. For example, in the group 3, 6, 6, 6, 6, 7, 8, 9, 10,
10, 11, the median is 7. Five numbers come before 7 in the list, and 5 come after. Remember it this way: