UPSC CDS II 2025 Mathematics Paper

X and Y are two alloys of copper (Cu) and zinc (Zn). Alloy X is prepared by mixing Cu and Zn in the ratio  5 : 4, and alloy Y is prepared by mixing Cu and Zn in the ratio 5 : 13 respectively. If equal quantities of alloys X and Y are melted to form a third alloy Z, then what is the ratio of Cu to Zn in Z?