82.14 will be rounded down to 80, 38.5 will be rounded up to 40, and 41.3 will be rounded down to 40.
80 + 40 + 40 = 160
The approximate sum is 160.
<span>This is a stratified random sample - the population was stratified by county, and then a random sample was selected within each county.stratified sampling is used for A government poll to determine who uses the state parks in missouri surveyed 50 people chosen randomly from each of missouri's counties.Stratified random sampling is a method of sampling that involves the division of a population into smaller groups known as strata. In stratified random sampling, or stratification, the strata are formed based on members' shared attributes or characteristics.</span>

It should be x=11 instead of x=-11, so
he is not correct because he made a sign error.
8 seconds
The hardest part of this is setting up the equation -- the calculations are pretty easy.
You're told that the time (needed to go from 0 to 100 MPH) is inversely proportional to the horsepower: what this means is that as horsepower gets larger, time gets smaller. This makes sense since the more horsepower you have, the less time it will take you to get to 100 MPH
You can think of this as:
200 HP = 10 seconds
250 HP = x seconds
You set the equation up as:
250 HP / 200 HP = 10 sec / x sec
Now, just cross multiply and solve:
250 / 200 = 10 / x
250x = (200 x 10)
250x = 2000
x = 2000 / 250
x = 8
So, as you increase the horsepower from 200 to 250, the time decreases from 10 seconds to 8 seconds.
Hope this helps!
Good luck.