For the set of numbers 2, 2, 4, 5 and 12, which of the following statements is true?

The mean of a set of seven numbers is 81. If one of the numbers is discarded, the mean of the remaining numbers is 78. The value if discarded number is

For which set of number do the mean, median and mode all have the same value?

If the arithmetic mean of 7, 5, 13, x and 9 is 10, then the value of x is

If the mean of five observations x, x+2, x+4, x+6, x+8, is 11, then the mean of first three observations is