Easy Math Tricks for Elementary School: Is a Number Divisible by …?
Yes it is. Any whole number divided by 1 is itself. Easy Math Trick #2: Is a Number Divisible by 2? If the last digit is 2, 4, 6, 8 or 0 the number is divisible by 2. For example, the last digit of the number 28,641 is 1, so the number isn’t divisible by 2. Easy Math Trick #3: Is a Number Divisible by 3? Add the digits together. If the sum of digits is divisible by 3, the original number is too. Not sure if the sum of digits is divisible by 3? Add up the sum’s digits and check if the new sum is divisible by 3. You can keep doing this until either you know the answer, or you end up with a single digit sum. If that sum is 3, 6, or 9, the original number is divisible by 3. For example, is the number 57,973 divisible by 3? Sum up the digits: 5+7+9+7+3=31. Since 31 is not divisible by 3, neither is 57,973. Not sure? Sum up the two digits of the sum 3+1=4, which isn’t divisible by 3. Taking another example, is the number 185,204,859 divisible by 3? Without a calculator it seems impossible to
