Answer:
The sample size required is at least 171
Step-by-step explanation:
We have that to find our 
level, that is the subtraction of 1 by the confidence interval divided by 2. So:
Now, we have to find z in the Ztable as such z has a pvalue of 
.
So it is z with a pvalue of 
, so 
Now, find the margin of error M as such
In which 
is the standard deviation of the population and n is the size of the sample.
What sample size is required?
A samle size of at least n is required, in which n is found when 
So
Rouding up
The sample size required is at least 171
Listening music and watching some movies
------------------------(- K)-------------0-------------(+K)-----------------
K unit to the left of 0, means K is negative.
The opposite of (-K) is (+K), both are symmetric vs. the origin "0", then its location will be +K
Average speed = total distance divided by total time.
In the first part, the car covered 490 km in 7 hours, but I think you mistyped the second part (“then covers a speed of 90km”) and a critical piece is missing to find the total distance and time.
