The range of temperature is the difference between the maximium value and the minimum value, in this case 78 - 41 = 37 F degrees. Note that it is not 37^oF.

You can do simple arithmetic in your head, but it is always a good practice to check your work especially if you turn it in for a grade. One way to check simple calculations is to use the calculator in Windows. Click on start at the bottom left corner of the screen and go up to Programs. Then go to Accessories and then to Calculator.

Click on the number 7, then 8. Click on the minus sign. Then click on 4, then 1. Click on the equals sign. You should see 37 in the window.

2. In a feeding study of pack rats, an ecologist weighed three rats. Their weights at the beginning of the study were 745.3g, 706.2g, and 724.8g. At the end of the study, their weights were 815.4g, 789.6g, and 774.7g, respectively. What were the changes in weight for each of the rats? What was the average weight change for all the rats?

3. Gasoline prices have fluctuated a lot recently. Two weeks ago, the price of unleaded gasoline was 125.9 cents per gallon. This week it is 137.9. What is the percent increase in gasoline price over this period?

The difference in price is 137.9 - 125.9 = 12.0 cents per gallon. The percent change is the change in price from the original, given as a percentage, or 100 * 12.0/125.9 = 9.53%.

4. What is the percent change in weight for each of the rats in question 2?

5. The rat scientist calculated that each week the rats in his experiment weighed 1.13 times their weight from the previous week. What is the instantaneous rate of growth for these rats?

The instantaneous rate of growth (or exponential growth rate) is found by taking the natural logarithm of the growth rate in a finite time period. In this case, it is = ln (1.13g/g/week) = 0.122g/g/week.

In the menu bar for the calculator, click on View, Scientific, to get additional functions. Click on 1, then the period, then 1, then 3. You should see 1.13 in the calculator window. On the left side of the calculator, click on ln. The ln function will give you the natural log of the number in the calculator window.

The reverse calculation is accomplished by using the inverse function. With the result from your previous calculation in the calculator window, click in the Inv box, then on the ln button. You should see the original 1.13.

6. A population of bacteria in a flask grows at an exponential rate of 0.47 individuals/individual/day. What is the ratio of the bacterial population from one day to the next?

7. In the 1920's, the population of deer on the Kaibab is reputed to have increased from one year to the next by a factor of 1.25 individuals/individual/year. What is the equivalent exponential rate of growth for this factor?

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