If the total cost of x apples is b cents, what is a general formula for the cost, in cents, of y apples ?

Question

ratios and proportions 

Answer 1

The unit cost, or cost of one apple, is (b cents)/(x apples).  So if one apple costs (b/x), then two apples costs (b/x)*2, three apples costs (b/x)*3, and y apples costs:

 

Cost = (b/x)*y cents