The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $240 and a standard deviation of $25. According to the Standard Deviation Rule, in a semester, almost all (99.7%) of the students spent on textbooks in a semester:.

The final part of the question is asking;

How much did all (99.7%) of the students spend on textbooks in a semester

almost all (99.7%) of the students spent between $165 and $315 on textbooks in a semester.

Step-by-step explanation:

The standard deviation rule describes to us that for distributions that have the normal shape, approximately 99.7% of the observations fall within 3 standard deviations of the mean.

In this question, we are given that; Mean = 240 and Standard deviation= 25

So, 3 standard deviation below the mean = Mean - 3(standard deviation)

= 240 - (3 × 25)

= 240 - 75 = 165

Now, 3 standard deviation above the mean = Mean + 3 standard deviation = 240 + (3 × 25)

= 240 + 75 = 315

So, almost all (99.7%) of the students spent between $165 and $315 on textbooks in a semester.

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