```Question 93978
When the yam is put into the oven, it is cooler than the oven. Therefore, to get a positive
answer to the difference in the temperatures, we have to subtract the temperature of the
yam from the 350 degree temperature of the oven.  Therefore, the temperature difference
should be written as (350 - H)
.
The constant of proportionality k then multiplies that temperature difference. So the rate
R is given by the equation:
.
{{{R = k*(350 - H)}}}
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The correct answer to your problem is the middle answer of the three you listed. The first
answer is incorrect because k does not multiply both the 350 and the H as it does in
our answer. And the last answer is incorrect because k will be positive and the difference
of H - 350 will be negative since the yam is cooler than the oven. So in multiplying
the constant k times (H - 350) you will get a negative answer, which indicates the rate is
negative ... meaning the yam is cooling off instead of heating up.  Obviously not correct.
.
Hope this helps you to analyze the problem.
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