John is driving to Denver.

Question

John is driving to Denver. Suppose that the distance to his destination (in miles) is a linear function of his total driving time (in minutes). John has 63

 miles to his destination after 40

 minutes of driving, and he has 48.6

 miles to his destination after 58

 minutes of driving. How many miles will he have to his destination after 70

 minutes of driving?

Answer 1

63 left after 40

48.6 left after 58

d=63+r40

d=48.6+r58

0 = 14.4 -18r

r = 14.4/18 = 7.2/9 = .8 miles per minute = .8(60)= 48 mph

d= 63 +.8(40) = 63 +32 = 95 miles = total distance

=48.6+.8(58) = 48.6+46.4 = 95

R = d-rt = 95-.8t

R(70) = 95 -.8(70) = 95-56 = 39 miles Remaining after 70 minutes