Let's list out what we already know:
Alexa's book is into 8 chapters
Rose's book is into 6 chapters
So since they are out of how many chapters, they number of chapters their books are split into will be the denominator of each fraction. Each girl has already read 3 chapters, so they'll have 3 as their numerator.
Alexa: 3/8
Rose:3/6
We can see that Rose is already at half of the book while Alexa's half would be 4/8, and she isn't there yet. So Rose read more of her book.

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3 years ago

The average life of a certain type of small motor is 10 years with a standard deviation of 2 years. The manufacturer replaces fr

taurus [48]

Answer:

A guarantee of 6.24 years should be offered.

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:

$\mu = 10, \sigma = 2$