how do you know if one is a factor of another without dividing.

Question

a) 4320 can be divided be divided by 2,5,10 evenly. How?

b)can 4230 be divided by 3 and 9?

c) can 98,022 be divided by 2,3,5,9,10? use divisibility rules.

I need help with these questions please i summed it up a little bit.

Answer 1

(a)
If the number is even, it is divisible by 2.
If the number ends with 0 or 5 (the last digit), it is divisible by 5.
If the number ends with 0, it is divisible by 10.

(b)
If the sum of the digits of a number is divisible by 3, it is divisible by 3. For instance, 4320: 4+3+2+0 = 9, and 9 is divisible by 3.
If the sum of the digits of a number is divisible by 9, it is divisible by 9. For instance, 4320: 4+3+2+0 = 9, and 9 is divisible by 9.

(c) Is 98022 divisible by
i. 2 ? -> Yes, cause it's even.
ii. 3 ? -> 9+8+0+2+2 = 21, and 21 is divisible by 3, so yes.
iii. 5 ? -> No it's not, cause it does not end with 0 or 5.
iv. 9 ? -> 9+8+0+2+2 = 21, and 21 is not divisible by 9, so no.
v. 10 ? -> No it's not, cause it does not end with 0.

Hope this helps~ :)

Answer 2

Thanks so much! it helped alot :D