How do i divide 72 into 2 groups so the ratio is 3 to 5?

Im not sure but ill try
3+5=8
72/8=9
9x5=45
72-45=27
9x3=27

The key to solve this kind of questions is:

1. add all sides of your ratio (3 + 5 = 8)
2. Divide the total by the sum you obtained in 1. So, (72 / 8 = 9)
3. Now times each side of your ratio with the answer you obtained in 2. So, 
3 * 9 = 27
and 5 * 9 = 45
Those are your two groups. To double check you can add 27 + 45 = 72.

Hope that helped!

Wow. that is a really cool question.