The median of the first four whole nubmers.

The median of the first 10 whole numbers is

There are four unknown numbers. The mean of the first two numbers is 4 and the mean of the first three is 9. The mean of all four number is 15, if one of the four number is 2 find the other numbers.

The mean deviation of the first 19 natural numbers about the median is

The sum of the first four terms of an A.P. is 56. The sum of the last four terms is 112. If its first term is 11, then find the number of terms.

If the product of the first four consecutive terms of a G.P is 256 and if the common ratio is 4 and the first term is positive, then its 3rd term i s ...........

Using the Rydberg formula , calculate the wavelength of the first four spectral lines in the Lyman series of the hydrogen spectrum .