Find the percent of her laps that are completed in less than 135 seconds. (Round your answer to two decimal places.)

Question

Terri Vogel, an amateur motorcycle racer, averages 129.71 seconds per 2.5 mile lap (in a seven-lap race) with a standard deviation of 2.28 seconds. The distribution of her race times is normally distributed. We are interested in one of her randomly selected laps. Find the percent of her laps that are completed in less than 135 seconds. (Round your answer to two decimal places.)

Answer 1

Mean = 129.71, SD = 2.28, Normally distributed.

P(X < 135) => z = (X - mean) / SD = (135 - 129.71) / 2.28 = 2.320175

use Z score table: .9898

or use Ti calculator (ti 84 plus)

2nd + vars, normal cdf, lower = 0, upper = 135, mu =129.71,sd = 2.28

Then, .98983433

Hence 0.99