If you add several normally distributed random numbers,the result is normally distributed, where the meanof the sum is the sum of the individual means, and thevariance of the sum is the sum of the individual variances.(Remember that variance is the square ofstandard deviation.) This is a difficult result to provemathematically, but it is easy to demonstrate withsimulation. To do so, run a simulation where you addthree normally distributed random numbers, each withmean 100 and standard deviation 10. Your single outputvariable should be the sum of these three numbers.Verify with @RISK that the distribution of this output isapproximately normal with mean 300 and variance 300(hence, standard deviation 300 17.32).