If b is a rational number, and x + b is rational, what must be true about x?

Aproduction manager test 10 toothbrushes and finds that their mean lifetime is 450 hours. she then design sales package of this type of toothbrush. it states that the customers can expect the toothbrush to last approximately 460 hours. this is an example of what phase of inferential statistics

Arandom sample of n = 25 observations is taken from a n(µ, σ ) population. a 95% confidence interval for µ was calculated to be (42.16, 57.84). the researcher feels that this interval is too wide. you want to reduce the interval to a width at most 12 units. a) for a confidence level of 95%, calculate the smallest sample size needed. b) for a sample size fixed at n = 25, calculate the largest confidence level 100(1 − α)% needed.

Jake volunteers to out his younger brother's basketball team in his free time. one of his tasks is to ensure that all the basketballs have enough air in them. given that a properly inflated basketball measures 8.8 inches across, what is the total volume of air inside six of jake’s basketballs? assume that the wall of each ball is infinitely thin.