Question 394276:  every 5 days Alma rides her skateboard in the park. Every 4 days she rides her bike to her friend's house.How often does Alma do both? 
 Answer by josmiceli(19441)      (Show Source): 
You can  put this solution on YOUR website! I could say that on a certain day, she starts counting days 
and, on the 4th day, she rides her bike. The next day, on the 5th day 
from the start day, she skateboards. 
The continuing counts are: 
8 days -bike 
10 days - skateboard 
----------------- 
12 days - bike 
15 days skateboard 
----------------- 
16 days - bike 
20 days - skateboard 
----------------- 
20 days - bike 
That's as far as I need to go. On the 20th day after she starts 
counting, she does both 
Now, every 20 days she does both 
Notice 20 is the smallest number that is evenly  
divisible by both 4 and 5 
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