Question

A maker has the opportunity to purchase several acres of land that is divided up into several lots for building single-family homes.

It is known that the average sale price of all of the lots is $80,000 and the standard deviation of the sale price is $12,000. What can you say about the percentage of lots that have selling prices between $56,000 and $104,000?
Choose one answer.

a)at most 25% of the selling prices lie in this interval
b.) at least 75% of the selling prices lie in this interval
c) approximately 99.7% of the selling prices lie in this interval
d) none of these

Answer 1

Here is a neat little applet that let's you do these kind of questions without even finding the z-scores first.

http://davidmlane.com/hyperstat/z_table.html

just enter 80000 as the mean, 12000 as the standard deviation, click on the "between" button and enter the range from your question.

I got .9545 or 95.5%