2:4= 1.5:3

2: 1.5=4:3

4:2=3: 1.5

4:3=2: 1.5

1.5:3=2:4

1.5:2=3:4

3: 1.5=4:2

3:4= 1.5:2

You need to determine 2×3= 1.5×4 first.

Then use this formula to convert.