To see if these ratios make a proportion let us first change them into fractions
= 4:10 = 4/10 = 4 ÷ 2 / 10 ÷ 2 = 2/5
= 6:15 = 6/15 = 6 ÷ 3 / 15 ÷ 3 = 2/5
= Since both these ratios are getting simplified into a same fraction , they are proportional .
Therefore , 4 : 10 :: 6 : 15 ( 4 : 10 is proportional to 6 : 15 )