Review of straight lines. During the period after birth, a male white rat gains

Question

Review of straight lines. During the period after birth, a male white rat gains exactly 40 grams (g) per week. (This rat is unusually regular in his growth, but 40 g per week is a realistic rate.)

A.) If the rat weighed 100 g at birth, give an equation for his weight after x weeks. What is the slope of this line?

B.) Would you be willing to use this line to predict the rat's weight at age 2 years? Do the prediction and think about the reasonableness of the result. (There are 454 grams in a pound. To help you assess the result, note that a large cat weighs about 10 pounds.)

Explanation / Answer

A)

y=40x+100

where x denotes the number of weeks

and y is the weight of male white rat(in grams) after x weeks.

The slope will be 40.

B)

After 2 years the weight obtained using the above linear regression will be much greater than realistic values. Lets check this out.There are 52 weeks in an year.

y=40x+100=40*2*52+100=4260 grams. = 9.38 pounds. This is clearly much higher than what we can normally get. Hence we will not use this line to predict for such long time period.

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