70, 75, 80, 85, 90, 105, 105, 130, 130, 130 The list shown consists of the times, in seconds, that it took each of 10

[Vincen]

70, 75, 80, 85, 90, 105, 105, 130, 130, 130

The list shown above consists of the times, in seconds, that it took each of 10 schoolchildren to run a distance of 400 on of meters. If the standard devastation of the 10 running times is 22.4 seconds, rounded to the nearest tenth of a second, how many of the 10 running times are more than 1 standard deviation below the mean of the 10 running times?

A. one
B. two
C. three
D. four
E. five

Answer: B

Source: GMAT Prep