Answer: 10 miles
Explanation:
If our car travels at 40 miles per hour, it travels 40 miles every 60 minutes. Since we are asked its distance at 15 minutes (which is 1/4 of 60) we can set up the proportion 40/60 = x/15. If we multiply 15x40 (600) and divide the outcome by 60, we get the final answer of 10 miles. We can also see that 15 minutes is 1/4 of 60 and just divide 40 by 4 to get our answer.