Running times for 400 meters are Normally distributed for young men between 18 and 30 years of age with a mean of 93 seconds and a standard deviation of 16 seconds. How fast does a man have to run to be in the top 5% of runners (quickest runner)?

The running time should at least 119.32 seconds to be in the top 5% of runners.

Step-by-step explanation:

Let X= random variable that represents the running time of men between 18 and 30 years of age.

As per given, X is normally distrusted with mean and standard deviation .

To find: x in top 5% i.e. we need to find x such that P(X<x)=95% or 0.95.

i.e.

Since, z-value for 0.95 p-value ( one-tailed) =1.645

So,

Hence, the running time should at least 119.32 seconds to be in the top 5% of runners.

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step-by-step explanation:

step-by-step explanation:

12: 00 p.m. to 7: 00 p.m. is a total of 7 hours.

4: 00 p.m. to 7: 00 p.m. is a total of 3 hours.

this means that from 4: 00 p.m to 7: 00 p.m. this represents 3/7 of what was lost from 12: 00 p.m. to 7: 00 p.m.

after knowing this, after doing 11,600 - 6,800 = 4,800

4,800 represents 3/7 of what was lost for 7 hours.

we then divide 4,800 by 3 which gets 1,600.

because we know that 1,600 represents 1/7 of how much water was lost, we just have to multiply by 7, which gets 11,200.   after adding 11,200 to how much water was left at 7: 00 p.m. which was 6,800. 11,200 + 6,800 = 18,000

this means that the pool originally had 18,000 gallons in the pool.

you can also check your work by doing 18,000 - 4(1600), which becomes           1800 - 6400 which gets you 11,600.