Finding the average rate of change? Need help!

I'm stuck in these two problems. What type of equations do I use for this? How do I plug in these numbers? Please help!

1. A car is advertised to go from 0 to 36 mph in 4 seconds. Find the average rate of change (i.e., the average acceleration) over that time.

2. Suppose your weight four years ago was 132 pounds and your weight today is 140 pounds. Find the average rate of change in your weight with respect to time.

1. Equation for velocity (v) and acceleration (a) with time (t)
v = a * t.

Now v = 36 mph or 36 / 3600 miles per second = 0.01 miles per second or 52.8 ft per second (since 1 mile = 5280 ft)

Substituting the values from above
52.8 per second = a * 4 seconds
a = 13.2 ft per second^2 (also equal to 0.0025 miles per second^2)

2. increase in weight = 8 pounds
the change happened over 4 years.

therefore the rate of change of weight = 8/4 = 2 pounds per year

Hope this helps

1. average acceleration = change in velocity / change in time
SO:
a = 36mph / 4sec
a = 9mph / sec

2. change in weight / change in time
= 140-132pounds / 4years
= 8pounds / 4years
= 2pounds / year