Answer: c = 0.0325d
==========================================================
Explanation:
For each row, divide the earnings over the sales.
- In row 1, we have 22/673 = 0.0327 approximately
- In row 2, we have 37/1298 = 0.0285 approximately
- In row 3, we have 101/3277 = 0.0308 approximately
- In row 4, we have 150/5180 = 0.0290 approximately
All of these decimal values have the following conversions to percentages
- 0.0327 = 3.27%
- 0.0285 = 2.85%
- 0.0308 = 3.08%
- 0.0290 = 2.90%
If we add up those percentages and divide by 4, we get the average percentage
(3.27+2.85+3.08+2.90)/4 = 3.025
So the average percentage of these four is 3.025%
So for instance, if you made $1000 in sales, then 0.0325*1000 = 32.50 would be the estimated earnings.
A good estimate in my opinion is the equation c = 0.0325d since 3.025% converts to the decimal form 0.0325
Another method you could use is linear regression to help estimate. Though this method is a lot more complicated involving many more steps. It's better to use technology (eg: graphing calculator) if you go this route. The linear regression line is approximately y = 0.02896x + 2.00732; we can see the slope 0.02896 isn't too far off from 0.0325. Other forms of regression are possible as well.
