Can you look at a number and tell right away if it’s divisible by another number? Well, it’s pretty easy for 2 – if it’s an even number, it’s definitely divisible by two. Testing whether a number is divisible by five is easy as well. How can you tell?
In this video, I’ll show you some tricks to determine if a number is divisible by 3, 4, 6 and 7 before you start to divide. Some are simple and fast and some are a bit more complex. These can be very useful tricks for working with larger numbers (or just really fun to play with for a bit).
These tricks are way cool and fun, but I would like to add one to the list: To see if a number is divisible by 9, simple add up the digits like you do for threes, and if they add up to nine (if you get a 2 digit number, add up those digits), the original number is divisible by nine!
Mary Crawford (age 12)