The average of the two-digit numbers, which remain the same when the digits interchange their positions, is-

The mean of 5 observations is 60, the mean of 10 observations is 30 and the mean of 15 observations is 20. The mean of a…

The average age of a class of 39 students is 15 years. If the age of the teacher is included, then the average increases…

The average of x numbers is y<sup>2</sup> and the average of y numbers is x<sup>2</sup>. So, th…

If the average of m numbers is n<sup>2</sup> and that of n numbers is m<sup>2</sup> , then the …

Average weight of 25 students of a class is 50 kg. If the weight of the class teacher is included , the average is incre…

The average income of A, B and C is Rs. 12,000 per month and average income of B, C and D is Rs. 15,000 per month. If th…

The average of seven numbers is 18. If one of the numbers is 17 and if it is replaced by 31, then the average becomes :