Question

An Uber ride costs a flat rate to start the ride and then charges an additional amount per mile. By the 3rd mile, the total cost of the trip is $9. By the 7th mile, the total cost is $17. What is the flat rate that Uber charges and how much does it cost per mile?

Answer 1

Step-by-step explanation:

the function is

ride cost c = mile rate r × miles m + flat rate f

c = r×m + f

now let's put the values in we know and solve for r and f :

9 = r×3 + f

17 = r×7 + f

now, since one term is the same in both equations, we use a simple trick for speed, and we subtract the whole first equation from the second :

17 = r×7 + f

- 9 = r×3 + f

-------------------

8 = r×4 + 0

r = 8/4 = $2

9 = 2×3 + f = 6 + f

f = $3

the first rate is $3, and it costs $2 per mile.