Question

The production cost $ C of a watch is partly constant and partly inversely as the number of watches n produced in an hour . When 250 watches are produced per hour , the production cost of each watch is $ 90 ; and when 500 watches are produced per hour , the production cost of each watch is $ 80 .
a ) Express C in terms of n .
b ) Find the cost , if 1000 of watches were produced .

Answer 1

C = a + b/w
Now you know that
a + b/250 = 90
a + b/500 = 80
Solve for a and b, then find C(1000)