Ratio and Proportion

The ratio of the number of girls to boys in class VIII is the same as the ratio of the number of boys to girls in class IX. The total number of students (boys and girls) in classes VIII and IX is 450 and 360, respectivel...

x : y : z = $\frac{1}{2} : \frac{1}{3} : \frac{1}{4}$ What is the value of $\frac{x+z-y}{y}$?

If p : q = 1 : 2 q : r = 4 : 3 r : s = 4 : 5 and u is 50% more than s, what is the ratio p : u?