An object is taken out of a 21 degree C room and placed outside where the temperature is 4 degree C. Twenty-five minutes later the temperature is 17 degree C. It cools according to Newton's Law. Determine the temperature of the object after one hour. Round to the nearest tenth of a degree.

The temperature of the object after one hour is 12.9°C to the nearest tenth of a degree

Step-by-step explanation:

Please see the attachments below

12.9 degree C

Step-by-step explanation:

1 hour = 60 minutes

So the Newton's law of cooling state that the rate of changing in temperature is proportional to the different in temperature, in other words:

where t is the time in minute, k is the cooling constant and is the environmental temperature. This differential equation can be solved to have a form of

where is the initial temperature.

We know that at 25 minutes T(25) = 17

So after 60 minutes:

(b) 240

step-by-step explanation:

first, we use the pythagorean formula using the given side lengths to find x. then we use x to find the side lengths. then we add the side lengths to find the perimeter.

pythagorean theorem formula:

a^2 + b^2 = c^2

(x - 20)^2 + (x - 40)^2 = x^2

x^2 - 40x + 400 + x^2 - 80x + 1600 = x^2

x^2 -120x + 2000 = 0

(x - 100)(x - 20) = 0

x - 100 = 0 or x - 20 = 0

x = 100 or x = 20

we see that the solution x = 20 must be discarded because it will give a negative side length and a side length of 0. the only valid solution is x = 100.

perimeter = sum of the lengths of the sides

perimeter = x + x - 20 + x - 40

perimeter = 3x - 60

replace x with 100.

perimeter = 3(100) - 60

perimeter = 300 - 60

perimeter = 240

other answer is correct. i had used the radius of the radius somehow. a website: