Question

A railroad crew can lay 7 miles of track each day. They need to lay 189 miles of track. The length, L (in miles), that is left to lay after d days is given by the following function.=L(d)=189-7dAnswer the following questions.(a)How many days will it take the crew to lay all the track?days(b)How many miles of track does the crew have left to lay after 17 days?miles

Answer 1

(a) 27 days

(b) 70 miles

Explanation:

Given that the track remaining to be laid is L(d) = 189 -7d, you want (a) the number of days to lay all the track, and (b) the amount remaining after 17 days.

(a) Total length

When the amount remaining is 0, the number of days that have elapsed is ...

0 = L(d)

0 = 189 -7d

7d = 189 . . . . . . add 7d

d = 27 . . . . . . . . divide by 7

It will take the crew 27 days to lay all the track.

(b) Remaining

The track remaining after 17 days is ...

L(17) = 189 -7(17) = 189 -119 = 70

70 miles of track remain to be laid after 17 days.

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