Hundred square

A hundred square has been printed on both sides of a piece of paper. What is on the back of 100? 58? 23? 19?

Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
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Problem



 

A hundred square has been printed on both sides of a piece of paper. One square is directly behind the other.

What is on the back of $100$? $58$? $23$? $19$?

Can you see a pattern?

 

12345678910
11121314151617181920
21222324252627282930
31323334353637383940
41424344454647484950
51525354555657585960
61626364656667686970
71727374757677787980
81828384858687888990
919293949596979899100

Click here for a poster of this problem.

 

This problem is also available in French: Grille de 100