Students of a Satara school play kabaddi, kho-kho, chess and carrom. How many students play exactly one of kabaddi and kho-kho (whatever else they play)?

Kabaddi but not kho-kho: $11+4+6+3=24$. Kho-kho but not kabaddi: $8+3+2+4=17$. Exactly one of the two $=24+17=41$. 51 also counts those who play both, 19 takes only the single-game parts $11+8$, and 31 misses the parts shared with chess or carrom.