The mean lifespan of a light bulb manufactured by a company is 400 days with a standard deviation of 23 days. Assuming that the light bulb's lifespan is a normally distributed random variable, what is the probability that a light bulb manufactured by this company will last at most 350 days? a)

0.015

b)

0.985

c)

0.083

d)

0.150

hello from mrbilldoesmath!

answer:

x - 3

discussion:

x^2 - 9 = (x-3) (x+3)   so

(x^2-9)/ (x + 3) = x-3

you,

mrb

in problems involving proportions, we can use cross products to test whether two ratios are equal and form a proportion. to find the cross products of a proportion, we multiply the outer terms, called the extremes, and the middle terms, called the means.

hope it