Use divisibility rules to find each missing digit. List all possible answers.?

Question

How would I find out how to do this? Will someone show me how? My son is in math, and it's been a while since I've done this. This [__] is a blank the gave in the homework.

1__2 is divisible by 9

1,__24 is divisible by 4

1, 25__ is divisible by 3

Answer 1

For anything to be divisible by 9, each number of the whole number, added together, must equal a number that is fully divisible by 9. For example, 549. 5+4+9=18, which is divisible by 9. For your question, all you need to do is to find numbers that will fit in the blank so that the numbers added together is divisible by 9. The only number that would fit in there would be a 6, because 1+2+6=9, and 9 is fully divisible by 9.

For a number to be divisible by 4, the last two digits must be divisible by 4. For example, 11,274,204. It may be a long number, but if you look at the last two digits, which is 04, it is certainly divisible by 4, so that means that long number must be fully divisible by 4. For your question, since the end of the number already ends in 24, which is divisible by 4, you can plug in any number, from 0-9.

For a number to be divisible by 3, the digits of the number must be added together, and it has to be divisible by 3. For example, 845. 8+4+5=17. 17 is not divisible by 3, so 845 is not divisible by 3. For your question, 1+2+5 already equals 8. If you add a 1 to the blank, the total amount of the digits is 9, which is divisible by 3. The other digits you can put in are 4 and 7.

Here is a source that can tell you more about more divisibility rules.

http://mathforum.org/dr.math/faq/faq.div...