Answer:
9 hours
Step-by-step explanation:
According to Newton's laws of cooling
dT/dt = -k(T - A)
Let U = T - A
dU/dT = 1
dU = dT
dt/dt = -kU
dT = -kU(dt)
dU/U = -kdt
On integration
ln(U) = -kt + C
U = Ce^-kt
T - A = Ce^-kt
T(0) = 68
T(5) = 25
68 - 20 = Ce^-k(0)
C = 48
and
25 -20 = 48e^-k(5)
5 = 48e^-5k
e^-5k = 5/48
-5k = ln (5/48)
k = - ln(5/48) / 5
k = - 0.4524
T - 20 = 48e^-0.4524t
When T = 21
21 -20 = 48e^-0.4524t
1 = 48e^-0..4524t
e^-0.4524t = 1/48
-0.4524t = ln (1/48)
t = - ln(1/48) / 0.4524
t = 8.5570
t= 9 hours ( to the nearest hour)
Answer: 17/24
Step-by-step explanation: Notice that 1/8 and 7/12 are unlike fractions. Our first step when adding unlike fractions is to get a common denominator.
The common denominator of 8 and 12 will be the least common multiple of 8 and 12 which is 24. To get a 24 in the denominator of 1/8, we multiply the numerator and the denominator by 3 which gives us 3/24. To get a 24 in the denominator of 7/12, we multiply the numerator and the denominator by 2 which gives us 14/24. Now we're adding like fractions.
3/24 + 14/24
To add like fractions or fractions that have the same denominator, simply add the numerators and keep the original denominator.
So here, if we add the numerators we have 3 + 14 which gives us 17. We put this over our original denominator which is 24. So we have 17/24.
So 1/8 + 7/12 is 17/24.
You can split this into 2 shapes.
1 of the shapes will be a small square. The dimensions for it would be 4 by 3 (12)
The second shape, the bigger rectangle has the dimensions, 12 by 6 (72)
Now add these two values 12+72 and you get, 84
you answer is A 84 square inches
Answer:
Y has to belong to the interval [-9,-2]
Step-by-step explanation:
-9≤y≤-2
