Liberal Arts Math/statistics

kygirl66 said:

1. At one high school, the mean time for running the 100-yd dash is 15.2 seconds with a standard deviation of 0.9 seconds. The times are very closely approximated by a normal curve. Find the percent of time that are: Between 14.3 and 16.1.

14.3-15.2/0.9=-0.9 =.-1.00= from z -score table is .341 or 34.1%
16.1-15.2/0.9=0.9=1.00 from z-score table is also .341 or 34.1%
add both together 34.1+34.1=68.2% round to 68%

2. Same question but: instead of 14.3 and 16.1 it request you from the percent that it will be greater than 16.1 seconds.
I am not sure where to start on this one. below x=16.1 is 34.1%+50%=84.1%
Above it lies the remainder


3. A jar of peanut butter contains 445g with a standard deviation of 10.2 grams. Find the probability that a jar contains more than 453g. Assume normal distribution. Use the z-score to rounded to 2 decimal places.

If you look up the z-score for 453, which is 8g above the mean, your z-value gives the probability
the jar contains less than or equal to this amount.
Expressing that as a percentage, subtract the result from 100%


453-445/10.2=8/10.2=0.7843 I know this is not right and need some assistance please.

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