Question

Craig Campanella and Edie Hall both have night jobs. Craig has every thirteenth night and Edie has every Fifth night off. How often will they have same night off?

Answer 1

Craig has every 13th night and Edie has every 5th night off.

You have to find LCM - the Least Common Multiple that is the smallest ("least") number that both 13 and 5 will divide into.

Since numbers 13 and 5 are both prime, then LCM(13,5)=13·5=65.

This means, they will have the same every 65th night off.