One gram of  an element ‘A’ combines with 2grams of an element ‘B’ to form a compound ‘X’. In another experiment two grams of element ‘A’ combine with six grams of an element ‘B’ to form compound ‘Y’ .  This data illustrates

(I) Compound ‘X’  :   1gm of ‘A’ + 2gms of ‘B’ = 1:2 ratio by mass(II) Compound ‘Y’ :   2gm of ‘A’ + 6gm of ‘B’  = 1:3 ratio by massDifferent weights of  ‘B’  combines with fixed weight of ‘A’  bear a simple ratio (2:3)This illustrates multiple proportions