Time is the independent variable
Nothing crazy here, just a matter of figuring out the limits of integration.



The answer to your problem would be 400 because to find the answer you need to multiply 120 by .3 to get the answer because 3 % means per 100 and that is why you make it .3 hope i help.
Answer:
There are 400 possible zip codes in the Houston area
Step-by-step explanation:
Here, we want to calculate the possible number of zip codes in the Houston area
We have 5 digits to form
77 is the first two digits ( this is fixed)
For the third digit, we are selecting 1 number out of 0,3,4 or 5
This means 4 C 1
The remaining digits can be any digits
We have 0-9, a total of 10 digits
The first will be 10 C 1 and the second last digit too is 10 C 1
So the number of possible zip codes will be;
4 C 1 * 10 C 1 * 10 C 1
= 4 * 10 * 10 = 400 possible zip codes