Solve 5[8-(9x-7)]+6x=0

Mathematics

1 answer:

evablogger [386]3 years ago

3 0

5[8-(9x-7)]+6x=0
5[8-9x+7]+6x=0
5[15-9x]+6x=0
75-45x+6x=0
75-39x=0
x=25/13

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The 68-95-99.7 rule states that, when X is an observation from a random bell-shaped (normally distributed) value with mean $\mu$ and standard deviation $\sigma$ , we have these following probabilities

$Pr(\mu - \sigma \leq X \leq \mu + \sigma) = 0.6827$

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The distribution of the number of months in service for the fleet of cars is bell-shaped and has a mean of 53 months and a standard deviation of 11 months

So $\mu = 53, \sigma = 11$

So:

$Pr(53-11 \leq X \leq 53+11) = 0.6827$

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-----------

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$Pr(31 \leq X \leq 75) = 0.9545$

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-----

What is the approximate percentage of cars that remain in service between 64 and 75 months?

Between 64 and 75 minutes is between one and two standard deviations above the mean.

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