You measure the lifetime of a random sample of 64 tires of a certain brand. the sample mean is x¯=50 months. suppose that the lifetimes for tires of this brand follow a normal distribution, with unknown mean µ and standard deviation σ=5 months, then a 99% confidence interval for µ is:

Two customers went to a post office. first customer paid $12 for 14 and 5 envelopes the second paid 24.80 for 10 postcards and 15 envelopes. what is cost of each envelope?

Show your workcan a right triangle have this sides? *how to prove it without using the pythagorean theorema*

Abag contains 3 red marbles, 2 blue marbles, and 2 green marbles. one marble is picked, then another marble. assume that the selections are made with replacement. a) find the probability of picking two red marbles with replacement. b) find the probability of picking a red marble and a blue marble. assume the selections are made without replacement. c) find the probability of picking two red marbles without replacement. d) find the probability of picking a red marble and a blue marble without replacement.