Answer : 4. "7 : 10"
Explanation :

Answer: D) 7 : 10 Explanation: Given 5:6 :: 7:10 :: 6:5 We know that compound ratio is calculated as a:b :: c:d :: e:f(axcxe):(bxdxf) => (5x7x6):(6x10x5)=> (210):(300)= 7:10