List of top Mathematics Questions on Variance and Standard Deviation asked in MHT CET

The standard deviation of the following distribution}

is

If both mean and variance of 50 observations $x_1, x_2, \ldots, x_{50}$ are equal to 16 and 256 respectively, then mean of $(x_1-5)^2, (x_2-5)^2, \ldots, (x_{50}-5)^2$ is

The variance of 20 observations is 5. If each observation is multiplied by 2, then variance of resulting observations is