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 .

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 .

oobleck · Accepted Answer

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)