48. Reading Rates The reading speed of sixth-grade students is approximately normal, with a mean speed of 125 words per minute a
2 answers:
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 and standard deviation
, the zscore of a measure X is given by:
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:
What is the reading speed of a sixth-grader whose reading speed is at the 90th percentile
This is the value of X when Z has a pvalue of 0.9. So it is X when Z = 1.28.
The reading speed of a sixth-grader whose reading speed is at the 90th percentile is 155.72 words per minute.
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Applying the distance formula, the perimeter of the plot of land, rounded to the nearest tenth, is: 482.8 ft.
<h3>What is the Distance Formula?</h3>Distance formula is given as: .
Name the coordinates of the plot of and as follows:
A (0, 120)
B (140, 100)
C (140, 20)
D (0, 0)
Perimeter of the plot of land = AB + BC + CD + AD
AD = |120 - 0| = 120 ft
BC = |100 - 20| = 80 ft
Use the distance formula to find AB and CD:
AB = √[(140−0)² + (100−120)²]
AB = √20000
AB = 141.4 ft
CD = √[(140−0)² + (20−0)²]
CD= √20000
CD = 141.4 ft
Perimeter of the plot of land = 141.4 + 141.4 + 120 + 80 = 482.8 ft.
Learn more about the distance formula on:
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