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let x be the random variable that represent the lenght of time it takes a student...

let x be the random variable that represent the lenght of time it takes a student to complete maths 23 exam. it was found that x has an approximately normal distribution with mean 1.5 hours and standard deviation =025 hours. (a) what is the probability that it takes at least 1.4 hours for a randomly selected student to complete the exam? (b) suppose 25 students are selected at random,what is the probability that the mean time x of completing the exam for these 25 students is no more than 1.4 hours?

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