probality questions

[Guest]

Hello, i am doing probability questions and i am stuck on these 3 questions. assistance would be much appreciated.

1)The average age of a vehicle registered in Canada is about 97 months and the standard deviation for the population is 15..
If a random sample of 45 vehicles is selected, find the probability (as percent) that the mean of their age is between 102 and 104 months.(Round your answer to the nearest whole percent)

2)The average monthly mortgage payment for recent home buyers in Winnipeg is \$725, with standard deviation of \$267. A random sample of 105 recent home buyers is selected.
Determine the probability (as percent) that their average monthly mortgage payment will be more than $772. (Round your answer to the nearest whole percent)

3)A study of oyster fishermen found that they catch an average of 34 kg of oyster per day with a standard deviation of 4 kg.
If a random sample of 34 fishermen is selected, what is the probability that their average catch is less than 34.5 kg? (Round your answer to the nearest whole percent)

[HallsofIvy]

I am puzzled by this. You say you are "stuck" on these problems which should mean that you have tried at least once to do each of these but you have not showed what you tried. If you would show what you tried, it would help to see what hints would help you.

"1)The average age of a vehicle registered in Canada is about 97 months and the standard deviation for the population is 15.."
Do you know what "standard deviation" means? It sounds like this problem is approximating the "age of vehicles registered in Canada" by a normal distribution with mean 97 months and standard deviation 15. Do you know what that means? It is much too difficult to calculate normal distribution "by hand". What you should do is reduce to the "standard normal distribution" and then look the probability up in a table (https://en.wikipedia.org/wiki/Standard_ ... 20above%2C) or using an app (http://byuimath.com/apps/normprob.html).