I dont understand what the question is asking
1 answer:
You might be interested in
Answer:
4 mph
Step-by-step explanation:
The average speed of an object is given by the total distance covered by the time taken:
where
d is the total distance covered
t is the time taken
in the first part, the person runs for 0.4 hours at a speed of 7 mph, so the distance covered in the 1st part is
Then the distance covered in the second part is , so the total distance is
(1)
The total time elapsed is 0.4 hours (first part) + 0.8 hours (second part), so
So we can write the average speed as
(1)
We want the average speed to be 5 mph,
v = 5 mph
Therefore we can rearrange eq.(1) to find d2:
And therefore, the speed in the second part must be
Answer:
a) Kenji's time had a lower z-score, which means that he is better compared to other runners on his level, and better to his peers compared to Nedda.
b) Rachel, because her time had the lowest z-score.
Step-by-step explanation:
Z-score:
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 question:
The lower the time, the better the runner is. So whoever's time has a lower z-score is a better runner. So initially, we find the z-score of each student's time.
An elementary school class ran 1 mile in an average of 11 minutes with a standard deviation of 3 minutes. Rachel, a student in the class, ran 1 mile in 8 minutes.
This means that for Rachel's time, we have that . So
A junior high school class ran 1 mile in an average of 9 minutes, with a standard deviation of 2 minutes. Kenji, a student in the class, ran 1 mile in 8.5 minutes.
This means that for Kenji's time, we have that . So
A high school class ran 1 mile in an average of 7 minutes with a standard deviation of 4 minutes. Nedda, a student in the class, ran 1 mile in 8 minutes.
This means that for Nedda's time, we have that . So
(a) Why is Kenji considered a better runner than Nedda, even though Nedda ran faster than he?
Kenji's time had a lower z-score, which means that he is better compared to other runners on his level, and better to his peers compared to Nedda.
(b) Who is the fastest runner with respect to his or her class? Explain why
Rachel, because her time had the lowest z-score.