The life of light bulbs is distributed normally. The standard deviation of the lifetime is 15 hours and the mean lifetime of a bulb is 530 hours. Find the probability of a bulb lasting for at least 561 hours.
+37084 561 is approximatly 2 standard deviations from mean: 530 + (2 x 15)....if you look at a bell curve this is the upper 2% of lightbulbs
so probability is 2/100 or 1/50
