If the population variance of the lifetime of a light bulb is 10000 hours, how large of a sample must be taken in order to be 99% confident that the margin of error will not exceed 35 hours

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The dimension of the rectangular pool shown below are 40 yards by 20 yards

Anew obstacle course is home to several new types of challenging obstacles. one such obstacle is traversing a 15-stair staircase. to make it more challenging, the stairs are not uniformly spaced. rather, the vertical space between consecutive stairs for the first 10 stairs is 113 feet and the vertical space for the last 5 stairs is 134 feet. what is the total vertical distance traveled ascending and descending the entire 15-stair staircase?