An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. if a sample of 30 bulbs has an average life of 780 hours, how large a sample is needed if we wish to be 96% confident that our sample mean will be within 10 hours of the true mean

christopher is 272,195 year old

step-by-step explanation:

second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.

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step-by-step explanation:

ever thing time 1 is a multiply by 1 it get  

where is the option given