Question

Buying paint in large quantities is often less expensive. Five 1-gallon buckets cost 25% more than a single 5-gallon bucket. Suppose that a job requires g gallons of paint. For what values of g should a 5-gallon bucket be purchased to minimize cost? Explain.

Answer 1

well, a 5-gallon bucket costs the same as 4 1-gallon cans.

So, if g <= 4, buy cans.
If 4<g<=5, but the bucket.

Naturally, if g > 5, buy enough buckets so that the remainder is less than 5. Then apply the above rule for the remainder.