Complete the three missing entries in the table

Question

Complete the three missing entries in the table:

Price of Gas($/gal)        Cost of Driving Jenna's Car($/mile)

2.00                                     ?
3.00                                   0.28
3.20                                     ?
3.50                                   0.31
4.00                                   0.33
4.50                                   0.35
  ?                                      0.40

Answer 1

We can use the changes from 3.50 to 4.00 and from 4.00 to 4.50 to determine that a 50 cent change in the price of gas per gallon is associated with a 2 cent change in the cost of driving the car. Therefore, it should be that when gas is 2 dollars per gallon, the cost of driving is 4 cents less than when the price is 3 dollars. if we increase the gas price by .2 from 3.00 instead of .5, we can use the fact that .2 is (2/5) of .5. Since the changes are proportional, we will therefore increase the price of driving by .8 cents. For the last one, we see that the increase in the cost of driving is .5 . Since .5 is 2.5 times .2, we know that we need to increase the price of gas by 2.5 *.50 or 1.25, so that the last price equals 5.75.