Challenge #1

Idea #150: Fruits

DISCLAIMER: You can engage you kid in part of the calculations involved in this challenge. This will teach him about exotic fruits and will give him an understanding about which fruits and veggies, money math and such. The only risk here is getting your your kid addicted to expensive fruits.

I will post my own findings on this challenge in: October 29, 2022.

The Fruits Challenge

[Updated in 08/09/2022 04:00 GMT-3]

This will be a different type of content we are posting here on the Vault of Ideas!

Previously, we have discussed Idea #150, that was about making a fruit salad that reduced the price per bowl. There is going to be a challenge about it.

The challenge is to find the best mix of fruits to put on a bowl to get the cheapest fruit salad possible.

I invite our dear visitors to brave with me this exercise; to find, with some ground rules laid out, the best mix of fruits for a fruit salad, in the most scientific way possible. Ultimately, we will compare prices per bowl of fruit salad. Of course, a direct comparison won't be possible because part of the work is raising out, any way you can, the prices of the fruits; this depends on where you are. But this can lead to an interesting comparison of prices of fruit salad, and fruits in general, among countries.

It is a well known fact that fruit prices shift from time to time, we say here in Brazil that fruits "come to season", meaning that sometimes there is plenty of them on the market so prices go down. Fruits actually are very complex products if you come to think about it. Sometimes a fruit is available throughout the year, sometimes only in certain months. Cherry for us is an example of this, because being a tropical country, we only get imported cherries around Christmas. To make matter worse, they spoil very quickly, and it is not unusual for it to be a lot of waste in this trade.

[An off-remark, in Colombia it is very common for you to get amazing fruit salad everywhere you go on market streets. This isn't a thing in Brazil, but I suspect that the person that brings this here would make tons of cash. Just as the first person who got those Mexican popsicles did. There is money to be made in making good regional products worldwide available, and this has been done since ancient markets.]


The ground rules for the challenge are:

  • A bowl of fruit salad has 250 grams.

  • A fruit salad has, at least, three types of fruits, at all times;

  • No individual fruit can make up less than 15%, in weight, of the fruit salad;

  • Before someone raises the "Is tomato a fruit question", a fruit here is only a thing that develop from seed-bearing structures of a plant. This does not include carrots, lettuces, broccoli, potatoes or onions, for example, that are edible structures of a plant, but not fruits (they are usually called vegetables). Tomato is considered a fruit, therefore. Sometimes we need to do a quick search about a specific one to get things straight.

  • With the previous consideration in mind, it is not the purpose of this exercise to start a witch hunt for people that mislabeled a veggie for a fruit. If you feel that there is a compelling nutritional reason for including a veggie into your fruit salad, you are allowed to make an excuse and add it, but it will be an extra item, not contributing to the minimum count of three fruits above. You will still need three real fruits plus your veggies.

  • For the purposes of this exercise, only fruits go into a fruit salad - no water, sugar, syrup, honey, cereals or cream, this sort of thing that can be added.

  • You can use common fruits or more exotic fruits, but you must honestly say these fruits are available to you where you live, at least during some part of the year;

  • In each month, there will be a different price of a bowl according to the fruit prices. We will compare the biggest of those prices throughout the year, to have an upper bound on price.

  • Additionally, we can compare plots of costs of bowl per year for each month*


If you want to go professional, these are some optional studies:

  • PRO Result #1: Make your fruit salad at home: is it edible? Tasty? Would it be something you could eat every morning?

  • PRO Result #2: Assuming you got a good result in the previous question, how many calories does your bowl have?

  • PRO Result #3: Estimate how many sugars, fibers and vitamins a person would ingest per bowl of your fruit salad (hard).

Get the spreadsheets going Note that you will need to estimate things such as weight of fruits. Best guesses and rough calculations are fair game, as long as you keep track of them somehow.

Who knows, you might get your kid selling perfect fruit salad instead of lemon juice!


After two months, I will post here my own results on the issue [after an honest attempt to round up to a fair number], so we can discuss it. But by all means, if you have conducted your own studies, share them on comments at any time.


* Provided I test that the comment service, DISQUS, accepts images.

Additional Information

Understanding the dynamics of this problem actually helps to deal with similar problems where you make a set or mix of products, of different manufacturing prices, and this is actually a problem worth solving. Who cares about fruits, anyway, lol.

Challenge Findings

Check out this Challenge Findings, here.

BANNER IMAGE CREDITS: ESA/Hubble & NASA, A. Filippenko, R. Jansen

Want to know more about this image? Follow this external link.