A dataset consists of five observations: $19, 15, 24, 26$ and $x$. If the median of the dataset is the same as the median of the three numbers: $24, 26,$ and $x,$ then the mean of the dataset is

The average marks in Maths exam of students in group A, group B and both the groups together are 80, 90 and 87 respectively. Which of the following cannot be the total number of students in the two groups?

The sum of deviations of 'n' observations about 25 is 25 and sum of deviations of the same 'n' observations about 35 is -15. Then the arithmetic mean of the observations is