Inside the box there are 20 coins of 1 or 2 values 

How much do they add up in total? 

Do you know for sure?

What has been your strategy?

This is a typical real-world situation where we don't have all the data for a problem. Normally, however, there is enough data to study it and approach or narrow down the answer.

Here we can illustrate this by breaking it down step by step:

  • Hi ha la mateixa quantitat de monedes 1 que de monedes 2? Són 10 monedes de cada classe?
  • Which currencies do there seem to be more?
  • We can see at the same time 5 coins, have they ever remained 5 equal?
  • De totes les possibles formes de fer 2 grups amb 20 monedes,  1 i 19, 2 i 18, 3 i 17, etc, quines podem descartar segur?
  • Of the possible options, which one has the highest value? How much would it be worth? 
  • Which has the lowest value? How much is it?