Do the ratios in each pair form a proportion?

Question

1) 1/3:3, 1/4:4
 
2) 2/3:2/9, 1/4:1/12
 
3) 4/5:1/2, 2/3:1/4

Answer 1

1) (1/3)*4≠3*(1/4), no (4/3)≠(3/4)

 

2) (2/3)*(1/12)=(2/9)*(1/4), both equal 1/18, yes

 

3) (4/5)*(1/4)≠(1/2)*(2/3), no (1/5)≠(1/3)