Question

The rockwell hardness of steel beams has a normal distribution with average 75 rockwells and with a standard deviation of 3.

a) The manufacturer wishes to find the specification of the steel beams so that 98% of the beams comply with the minimum hardness. this is only 2% of the time it does not comply with the minimum hardness. b) If a client wants to buy 2500 steel beams and wants the beams to have a hardness greater than 73 rockwells. What is the expected number of beams that will meet the client's needs?

c) If we increase the thickness of the steel 3 times and give it a heat treatment, the new test piece will have a hardness three times the previous hardness plus 40 rockwells. What is the probability that the new test piece has a hardness greater than 250 rockwells.

Answer 1