Chapter 6B - Answers

1. Rate or slope and the initial point. These may be found given any two points.

2. H = 100t + 9100 where H = Height on the ski lift (feet) and t = time (min.).
   H = 9100 at t = 0 (i.e. ski base is at 9100 feet)

3. d = -$\frac{4}{3}$t + 70 where d = depth (in.) and t = time (days).
   d = 0 at 52.5 days

4. PA = .15t; PB = .10t + 4.95 where PA and PB are the cost of plans A and B, respectively, t is the number of minutes spent on calls.

   When does PA = PB? at $t$ = 99 minutes. So for Plan B to be worth it you would need to talk for at least 100 minutes. Drawing a graph of the two functions would be helpful.

5. Profit = Revenue - Cost
   C = 0.25h + 1000 where h is the number of hotdogs and C = cost in $
   R = 1.50h where R = revenue in $ and h is as above.

   Thus, P = R - C = 1.25h - 1000 where P = profit in $.

   How many hotdogs to break even (i.e. P = 0)? h = 800 hotdogs.

   Selling 50 hotdogs a day, means 16 days to break even.