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# Ratio and Proportion : Elk and Fuel Efficiency

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1. Park rangers catch, tag, and then release 140 elk back into a national park. One month later, they select a sample of 130 elk, 91 of which are tagged. Assuming the ratio of tagged elk in the sample holds for all elk in the park, approximately how many elk are in the park?

2. The formula M = 0.0075x2 - 0.2676x + 14.8 models the fuel efficiency of passenger cars, M, in miles per gallon, x years after 1940. Environmentalists pressured automobile manufactures for a fuel efficiency of 45 miles per gallon by the year 2000. In which year will the fuel efficiency reach 45 miles per gallon according to the formula?

##### Solution Summary

Ratio and proportion problems are solved.

Solution provided by:
###### Education
• BSc , Wuhan Univ. China
• MA, Shandong Univ.
###### Recent Feedback
• "Your solution, looks excellent. I recognize things from previous chapters. I have seen the standard deviation formula you used to get 5.154. I do understand the Central Limit Theorem needs the sample size (n) to be greater than 30, we have 100. I do understand the sample mean(s) of the population will follow a normal distribution, and that CLT states the sample mean of population is the population (mean), we have 143.74. But when and WHY do we use the standard deviation formula where you got 5.154. WHEN & Why use standard deviation of the sample mean. I don't understand, why don't we simply use the "100" I understand that standard deviation is the square root of variance. I do understand that the variance is the square of the differences of each sample data value minus the mean. But somehow, why not use 100, why use standard deviation of sample mean? Please help explain."
• "excellent work"
• "Thank you so much for all of your help!!! I will be posting another assignment. Please let me know (once posted), if the credits I'm offering is enough or you ! Thanks again!"
• "Thank you"
• "Thank you very much for your valuable time and assistance!"

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