Not sure how to do these 3 problems Scores on the ACT exam are on average 21 wit

Question

Not sure how to do these 3 problems

Scores on the ACT exam are on average 21 with standard deviation of 4. Find the probability that a student taking the ACT exam scores at most 18. Round your answer to 4 decimal places. Question9 1 pts Cherry trees in a certain orchard have heights that are normally distributed with mean 112 inches and standard deviation of 14 inches. What proportion of these trees are between 113 and 115 inches tall? Round your answer to 4 decimal places. Question 10 1 pts The actual weights of 12 oz bags of ground coffee can reasonably be modeled by a normal distribution with mean of 12.1 oz and standard deviation of 0.08 oz. What percentage of bags are underfilled? Round your answer to 2 decimal places.

Explanation / Answer

Q1) P(X<18)

=P(Z<(18-21)/4

= P(Z<-0.75)

= 0.2266

Q2) P(113<X<115)

= P((113-112)/14<Z<(115-112)/14)

= 0.0564

Q3) P(X<12)

= P(Z<(12-12.1)/0.08)

= P(Z<-1.25)

= 10.56%

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