Numerical - Mean & standard deviation for margin of safety

Q.  A plain carbon steel has mean yield strength of 300 N/mm2 and standard deviation of 50 N/mm2. What is the mean and standard deviation of margin of safety, if mean tensile stress of 250 N/mm2 and standard deviation of 65 N/mm2 acts on it?
- Published on 18 Sep 15

a. 23.45 N/mm2, 50 N/mm2
b. 50 N/mm2, 82 N/mm2
c. 82 N/mm2, 7.07 N/mm2
d. 7.07 N/mm2, 50 N/mm2

ANSWER: 50 N/mm2, 82 N/mm2

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