Rotorburners, I need your help! Ordinarily I'd go see a tutor about this sort of thing, but drop-in sessions are booked up for almost a fortnight, and I really don't want to fall that far behind - so I'm appealing to RB's academic collective to give me some support!
I'm not necessarily after answer's, but some sort of explanation of how I'd approach and work through the multiple associated questions would be helpful. And because you'll be doing the job that someone else would ordinarily be paid to do, I'll throw in a reward
The time the average punter spends mountain biking over 3 years varies according to a distribution that is approximately normal with a mean of 400 days, and a standard deviation of 30 days.
What is the probability that a randomly selected punter will ride less than 380 days?
What percentage of riders get out on the trails between 380 and 420 days?
Between what values do the amount of days of the middle 85% fall?
In the above question, a range of 85% has been determined. What is the probability that 15 randomly chosen riders will all get out on the trails in in that 85% range?