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Phantasy [73]
3 years ago
9

NEED HELP ASAP laboratory tests show that the lives of light bulbs are normally distributed with a mean of 750 hours and a stand

ard deviation of 75 hours. find the probability that a randomly selected light bulb will last between 900 and 975 hours.
Mathematics
1 answer:
professor190 [17]3 years ago
8 0

Answer:

0.0214

Step-by-step explanation:

We can get these answer by finding the z-scores at first

Mathematically;

z-score = x-mean/sd

For 900;

z-score = 900-750/75 = 150/75 = 2

For 975

z-score = (975-750)/75 = 3

So the probability we want to calculate is;

P(2<x<3)

This can be calculated using the standard normal distribution table

From the standard score table;

P(2<x<3) = 0.0214

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Answer:

5 \frac{5}{8} cups

Step-by-step explanation:

Given: A baker is using a cookie that calls for 2 \frac{1}{4} cups of flour to yield 36 cookies.

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Let's convert 2 \frac{1}{4} to improper fraction.

2\frac{1}{4} = \frac{(2*4) + 1}{4} = \frac{9}{4}

Let "x" be the amount flour to make 90 cookies

<u>Amount of Flour</u>                 <u>Number of cookies</u>

 \frac{9}{4}                               36

       x                                            90

Now form a proportion.

\frac{\frac{9}{4}}{x} = \frac{36}{90}

Now let's cross multiply, we get

\frac{9}{4} *90 = 36x\\\

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Now let's simplify the fraction part, Here the GCF of 90 and 144 is 18, so dividing the fraction's numerator and the denominator by 18, we get

x = 5 \frac{5}{8} cups

So the baker needs 5 \frac{5}{8} cups to make 90 cookies.

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