Question

A truck driver is d(t) = 400 − 70t miles from his destination after driving t hours. He drives at a constant rate.

(a) Interpret the ordered pair (4, 120). When the driver has driven ____hours, he is Incorrect: ____. miles from his destination.

(b) After driving 2 hours, how far is he from his destination? mi

(c) How far did he go in his second hour of driving? mi

Answer 1

a. 4 and 120. b. 260 miles. c. 140 miles.

Explanation:

d(t) = 400-70t.

a. (4,120) refers that with t=4 (when the driver has driven 4 hours), he is incorrect: 120 miles from his destination. d(4) = 400-70(4) = 400-280 = 120.

b. After driving 2 hours, that is in t=2, he is d(2)= 400-70(2) = 400-140 = 260 miles from his destination.

c. In his second hour of driving, that is in t=2 he is 260 miles from his destination, so he has driven 140 miles.