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What is the standard deviation of the following data set rounded to the nearest tenth? 3, 17, 18, 15, 12, 21, 9

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)

Savannah is painting a striped background for a mural on a wall that is 1515 yards long. she wants a total of 9696 stripes that are all the same width. which calculation should savannah use to decide how wide to make each stripe?