Question

Suppose that 18 inches of wire costs 90 cents. At the same rate, how much (in cents) will 15 inches of wire cost?

Answer 1

18 inches cost 90 cents

The porportion is inches / cents = 18/90

For 15 inches of wire: 15/x, where x is the cost of 15 inches of wires in cents.

So, equal both:

18/90 =15/x

Solve for x:

x = 15 / (18/90)

x= 75 cents