Question

The cost of a car service us partly constant and partly varies with the time it takes to do the work. It costs #3500 for a 5 and half hours service and #2900 for a 4 hours service, find the formula connecting cost, #C You with time, T hours.

Answer 1

c = b + r t
3500 = b + r (5.5)
2900 = b + r (4.0)
-------------------------- subtract
600 = 1.5 r
r = 400
go back and get b

Answer 2

C=a+bT(where a and b are constant). 3500=a+5.5b......(1). 2900=a+4b.........(2) (2)-(1). 600=1.5b. b=600/1.5

Answer 3

b=400.

Substitute b=400 in equation (1)

3500=a+5.5(400)

3500=a+2200

a=1300

Therefore, the formula connecting cost (C) with time (T) is:

C=1300+400T