2021 WSMO Speed Round Problems/Problem 6

Problem

A bag weighs 1 pound and can hold 16 pounds of food at maximum. Danny buys 100 packages of tomatoes and 300 packages of potatoes. Tomatoes come in packages that are $12$ ounces each and potatoes come in packages that are $24$ ounces each. If all of Danny's food must go in bags, how many pounds does Danny's total luggage weigh, including the bags? (Danny will use only as many bags as he needs).

Solution

Because bags weigh multiples of $12$ ounces, a bag can hold at most $252$ ounces, meaning that Danny uses at least $\frac{8400}{252}=\frac{100}{3}$ bags, or $34$ bags. A construction is to let the first $33$ bags have $9$ packages of tomatoes and $3$ packages of potatoes, while the last bag has $3$ packages of tomatoes and $1$ package of potatoes.

(We cannot use $33$ bags because this construction is not valid!)

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2021 WSMO Speed Round Problems/Problem 6

Problem

Solution