20% of 80 = 40% of ________ ?
1 answer:
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Answer:
x = 63.6
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 and also the area to its left. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X, which is the area to its right.
In this problem, we have that:
Find a value of x that has area 0.01 to its right
This is x when Z has a pvalue of 1-0.01 = 0.99. So it is X when Z = 2.3267.
So x = 63.6