Answer:
It will take 4 minutes and 30 seconds for hot coffee to cool to a temperature of 25 ° C
Step-by-step explanation:
This problem can be modeled by a first order equation
T(t) = TA + kt
In which TA is the temperature at instant zero and r is the rate of warming(g>0) or cooling(k<0). t is the time in minutes.
The initial temperature of the cup of coffee is 70ºC. So TA = 70. The temperature cools at the rate of 10ºC per minute, so k = -10. So, the equation of the model is:
T(t) = 70 - 10t
We want to know the instant of time when T = 25, so:
25 = 70 - 10t
10t = 70 - 25
10t = 45
t = 4.5 minutes
It will take 4 minutes and 30 seconds for hot coffee to cool to a temperature of 25 ° C
Answer:
16
Step-by-step explanation:
Use the method of PEMDAS (Parenthesis, Exponent, multiplication, division, addition and then subtraction.)
When using this order you would do 10-9 first
23 + 5 * (10-9) - 12
23+ 5 * 1 - 12
then 5 times 1
23 + 5 * 1 - 12
23 + 5 - 12
then 23 + 5 and subract 12 from the solution
23 + 5 - 12
28 - 12 =
16
Answer: of what?
Step-by-step explanation:
Answer:
25
Step-by-step explanation:
he got an 80 so if that was his grade by answering 20 questions right then the correct answer would be 25 questions
Answer:
Length: 40 inches
Width: 10 inches
Step-by-step explanation:
Let 
width of the rectangle.
From the information "length of a rectangle is four times its width", we can express the length as:
Length = 
- - - -
Perimeter = 
(formula for perimeter of rectangle)
(combine like terms)
inches
∴ The width of the rectangle is 10 inches.
To find the length of the rectangle, we can use substitution:
Length =
inches
∴ The length of the rectangle is 40 inches.
Hope this helps :)
