Decrease = (original number - new number) / original number .....x 100
decrease = (49 - 22) / 49.....* 100 =
(27 / 49) * 100 =
2700 / 49 = 55% decrease

4 0

3 years ago

48. Reading Rates The reading speed of sixth-grade students is approximately normal, with a mean speed of 125 words per minute a

son4ous [18]

Answer:

The reading speed of a sixth-grader whose reading speed is at the 90th percentile is 155.72 words per minute.

Step-by-step explanation:

Problems of normally distributed samples are solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$ , the zscore of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

In this problem, we have that:

$\mu = 125, \sigma = 24$