Math Problem: Better buy on cheese

You’re in the grocery store on April 24th and you need cheddar, desperately. Upon reaching the back of the store you discover that there is a sale!

Excitedly, you search the shelves and find a 500g package of old, light cheddar (your favourite) for only $3.99. Beside it is a 340g package of the same cheese; it’s $2.99.

Looks simple at first, but then you see the expiration dates: May 3rd for the 500g package and May 19th for the 340g package.

Last time you bought the 500g package it took your family two weeks to eat it.

What should you buy?

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2 thoughts on “Math Problem: Better buy on cheese

    • Here are my thoughts on the problem. There isn’t a single right answer, of course. There are some big assumptions in my solution.

      If you were to eat the same amount of cheese each day, you would eat about 35.7g/day (500g/14 days).

      Assuming you eat some cheese upon returning home on April 24th, you would consume 321.4g by the end of May 2nd, when the 500g brick expires. The 340g brick would not have expired in this time.

      So, on May 2nd you would have spent either $3.99 or $2.99 to consume 321.4g of cheese. If you bought the 340g brick, you still have another half-day or so of cheese in the fridge, and you’ve saved a buck.

      In fact, you can safely polish off a second brick of 340g before the May 19th expiry date. You might consider buying two of the smaller bricks (for $5.98) instead of a single “clearance” 500g brick.

      Alternatively, you could have Ravioli Au Gratin on May 2nd and use it all up. :)

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