What is Surya's age? I. Surya and his sister are

Solution

Statement 1- Surya and his sister are the only children in Ramesh's home. It means there are only two children in Ramesh's home. Nothing mentioned about their ages. Statement 2. Surya's sister is elder to him by 5 years. It means if we have Surya's age then we can find his sister's age or if we have sister's age then we can find Surya's age Statement 3- Surya's sister just turned 15 this year. Here Surya's sister age is given. By combining Statement 2, 3 we can say that Surya's age is 5 years less than his sister, and sister's age given is 15 So, Surya's age is 10. Hence, Statement 2,3 are sufficient.