# Random Variables- Properties of Variance/Standard Deviation

A mason is contracted to build a patio retaining wall. Plans call for the base of the wall to be a row of 50 10-inch bricks, each separated by ½ inch thick mortar. Suppose that the bricks used are randomly chosen from a population of bricks whose mean length is 10 inches and whose standard deviation is 1/32 inch. Also suppose that the mason, on the average, will make the mortar ½ inch thick, but the actual dimension varies from brick to brick, the standard deviation of the thickness being 1/16 inch. What is the standard deviation of L, the length of the first row of the wall?

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We know that if the length of bricks and thickness of mortar are all independent random variables, we have the following ...

#### Solution Summary

Properties of variances and standard deviations are examined.