Did u attach a pic to this?
The tail of the train starts one mile from the mouth of the tunnel and it must travel that distance plus the length of the tunnel in 3 minutes.
Let t = tunnel length
t + 1 = distance the tail must travel in 3 minutes.
3 minutes = 1/20 hr
(t+1) miles / 60 m/hr = 1/20 hr
t + 1 = 60/20
t+1 = 3
Subtract 1 from each side:
t = 2
The tunnel is 2 miles long.
4.
4x - 36 = 2*(x+7) => 4x - 36 = 2x + 14 => 4x - 2x = 50 => x = 25 => DG = 4*25 - 36 = 64.
Answer:
a. Decay
b. 0.5
c. 4
Explanation:
If we have a function of the form

then
a = intital amount
b = growth / decay rate factor
x = time interval
If b > 1; then the equation is modelling growth. If b < 0, then the equation is modelling decay.
Now in our case, we have

Here we see that
inital amount = a = 4
b = 1/ 2 < 0, meaning the function is modeling decay
decay factor = b = 1/2
Therefore, the answers are
a. Decay
b. 0.5
c. 4