1. ## Calculus Question

I do not know how to find part b of this problem can anyone help me.

When a cold drink is taken from a refrigerator, its temperature is 5°C. After 25 minutes in a 20°C room its temperature has increased to 10°C. (Round the answers to one decimal place.)
(a) What is the temperature of the drink after 35 minutes?
°C

(b) When will its temperature be 16°C?
minutes

2. Originally Posted by skeltonjoe
I do not know how to find part b of this problem can anyone help me.

When a cold drink is taken from a refrigerator, its temperature is 5°C. After 25 minutes in a 20°C room its temperature has increased to 10°C. (Round the answers to one decimal place.)
(a) What is the temperature of the drink after 35 minutes?
°C

(b) When will its temperature be 16°C?
minutes
I assume the green check means you got part (a) correct ... how did you figure that value?

3. i did the problem out, then for part b I know your suppose to take like 16=20 - 16 * 2/3 raised to the t/25 and solve it for t which I get 85.5 but apparently its wrong.

4. Originally Posted by skeltonjoe
i did the problem out, then for part b I know your suppose to take like 16=20 - 16 * 2/3 raised to the t/25 and solve it for t which I get 85.5 but apparently its wrong.
perhaps I wasn't clear in my request ...

what equation did you use to solve part (a) , and how did you go about getting that equation?

5. y(t) = -15 * 2/3 ^ t/25

I keep getting 85.5 I just redid it 3 times

6. Originally Posted by skeltonjoe
y(t) = -15 * 2/3 ^ t/25

I keep getting 85.5 I just redid it 3 times
your equation is incorrect. if y is the temperature, then ...

y(0) should = 5

y(25) should = 10

your equation does not yield those values for the given times.

you should be deriving the temperature function from Newton's law of cooling/heating ...

$\displaystyle \frac{dy}{dt} = k(20 - y)$ , using the initial conditions y(0) = 5 and y(25) = 10

7. Originally Posted by skeltonjoe
y(t) = -15 * 2/3 ^ t/25

I keep getting 85.5 I just redid it 3 times
Did you mean $\displaystyle y(t)=20-15(\frac{2}{3})^{\frac{t}{25}}$ ?

8. yes thats what I meant, can anyone please answer this question its due in 2 hours

9. i got it the answer was 81.5