Question

in which story could you use the quotient 90 ÷ 2\frac{1}{2} to answer the question?

valentina puts a turkey in the oven to roast. after a few minutes, she remembers to add a thermometer. at that time, she notes that the turkey’s temperature is 90°f. she takes the turkey out once it reaches 160°f. if the turkey was in the oven for about 2\frac{1}{2} additional hours, how much did its temperature increase per hour on average during that time?

before putting a turkey in the oven to roast, valentina adds a thermometer. at that time, she notes that its temperature is about 70°f. she takes the turkey out once it reaches 160°f. if the turkey was in the oven for about 2\frac{1}{2} hours, how much did its temperature increase per hour?

Explanation:

Step1: Recall the formula for average rate

The formula for average rate of change is $\frac{\text{Change in quantity}}{\text{Time}}$. To use $90\div2\frac{1}{2}$, the starting - point related quantity should be 90 and the time is $2\frac{1}{2}$ hours.

Step2: Analyze the first story

In the first story, the starting temperature is 90°F, but to find the average temperature increase per hour, we need to first find the change in temperature which is $160 - 90=70$°F. The operation to find the average temperature increase per hour is $\frac{160 - 90}{2\frac{1}{2}}=\frac{70}{2\frac{1}{2}}$, not $90\div2\frac{1}{2}$.

Step3: Analyze the second story

In the second story, we are not given any operation related to 90. The starting temperature is 70°F, and the operation to find the average temperature increase per hour is $\frac{160 - 70}{2\frac{1}{2}}=\frac{90}{2\frac{1}{2}} = 90\div2\frac{1}{2}$.

Answer:

The second story.