Question

Hiw do i use mental math to determine if a ratio is simplified?

Answer 1

You can look at it as if it were a fraction or leave it as it is. You then see if one of the numbers shares a factor with the other. Here are so examples:

3:4 This ratio is in simplest form because you can no longer simplify the number 3 by anything.

5:30 This ratio can be simplified because 30 can be divided by 5, the final answer would be 1:6. You get to this answer by dividing both 5 and 30 by 5 which makes the final answer 1:6.

2:12 This ratio can be simplified because 12 can be divided by 2, the final answer would be 1:6.

I hope this answer helps, it would be easier to teach you if it were face to face, again sorry if this isn't what you were looking for! :)

Answer 2

See if the top and bottom are both divisible by a common factor.
5/15 can be simplified to 1/3 because the top and bottom are divisible by 5.
If you know your divisibility rules, this should be easy.
Also worth noting: You only need to check if it's divisible by primes. If it's not divisible by 2, it won't be divisible by 4, because 2 is a factor of 4.