Explain why any number that is divisible by 9 is also divisible by 3.

Explain why any number that is divisible by 9 is also divisible by 3.

Tutors, please sign in to answer this question.

Since 9 = 3 * 3, 9 is divisible by 3. By extension, 3 would be a factor of any number divisible by 9.

Let's look at an example - say, 72.

We know that 9 * 8 = 72. Now, since 9 = 3*3, we can replace 9 in our example to get 3*3*8 = 72, which shows that 72 is divisible by both 9 and 3.

John K.

Ardent Mathematics, Science, History, SAT and German Polymath

East Elmhurst, NY

5.0
(65 ratings)

Richard B.

Effective and Experienced Math and Science Tutor and Teacher

South Orange, NJ

5.0
(195 ratings)

Alex C.

Harvard/MIT Finance and Statistics Tutor

Fort Lee, NJ

5.0
(165 ratings)

## Comments

Also a neat little trick is if the digits add up to a number divisible by 3 then the number is divisible by 3. EX: 7+2=9 so 72 is divisible by 3. or 15 1+5=6 so 15 is divisible by 3. This little trick will help you when you need to factor numbers.