



 
Hi Samuel, 4 times 4 is sixteen and sixteen is three times 5 plus one. Thus in base 5 $4 \times 4 = 31_5$ not $13_5 .$ $13_5$ is one five and three more which is eight. If you go to the Quandaries and Queries page on Math Central and use the Quick Search to search for the term base 5 you will find some worked examples and explanations of the procedures. Penny  


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