I really need help!!

zaimba6 said:

I'm just so stuck on this one that I can't even start it. For some reason I have a feeling 1a. is kind of a 'trick' question, where the answer is in the first paragraph. I have a feeling the answer is 65kg, but hey, I could be wrong. I think word questions just freak me out, I'd much rather have to solve an equation than this jumble of words....

1. A lift in a building carriers 25 passengers. The weights of single passengers chosen at random have a mean of 65 kilograms and a standard deviation of 7 kilograms.

a. Calculate the mean of the total weights of the passengers.

b. Calculate the variance of the total weight of the 25 passengers

2. Nuts and bolts are used in the assembly of a part of the lift. The diameters of both nuts and bolts are normally distributed. The diameters of nuts vary randomly with a mean of 15.3 millimeters and standard deviation of 0.2 millimeters. The diameters of the bolts also vary randomly with a mean of 15.2 millimeters and a standard deviation of 0.1 millimeters.

a. Calculate the mean difference between the diameter of the nuts and the diameters of the bolts.

b. Calculate the variance of the difference between the diameter of the nuts and the diameter of the bolts.



Can you please give answers step by step and explain what you are doing.

Thanks so much!

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Subhotosh Khan said:

I don't understand what is referenced by "mean of the total weights of the passengers."

Please read the post titled "Read before Posting".

We can help - we only help after you have shown your work - or ask a specific question (not a statement like "Don't know any of these")

Please share your work with us indicating exactly where you are stuck - so that we may know where to begin to help you.

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