The compound ratio of ratios a:b and c:d is ac:bd. ⇒9x:2y=3:4 ⇒x∕y=2∕9×3∕4 ⇒x∕y=1∕6 Similarly, Compound ratio of ratios (x+y):5 and 2:y=2∕5×(x+y)∕y=2∕5×(x∕y+1) Substituting from (1), ⇒ Compound ratio of ratios (x+y):5 and 2:y=2∕5×(1∕6+1)=2∕5×7∕6=7∕15 ∴ Compound ratio of ratios (x+y):5 and 2:y=7:15