The mean of n observations is . If each observation is multiplied by k, the mean of new observations is

Which one of the following is not a measure of central value?

The mean of n observations is . If k is added to each observation, then the new mean is

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?