cost of manufacturing notebook is inversely proportional to the number produced. When 16000 notebooks are produced it costs .60. What is the cost of each notebook when 12000 are produced?

Question

not sure how to solve this

Answer 1

kost=x/16,000=0.6

x=16,000*0.6=9,600

at 1200, kost=x/1200=9600/1200=8

Answer 2

Cost C=a/N where a is a constant of proportionality and N is the number of notebooks.

When C=0.60, N=16000 so a=0.60*16000=9600.

So C=9600/N. When N=12000, C=9600/12000=0.80.

Another way to do it is to use the fraction 16000/12000=16/12=4/3. We know that the cost increases as the number of notebooks decreases and vice versa. So we expect the cost for 12000 notebooks to be higher than 0.60, therefore we need a fraction that's greater than 1 to multiply by, i.e., 4/3 not 3/4. And 0.60*4/3=0.20*4=0.80.