Average time needed..

Dear Talk Stats users,

First of I'm glad I found this forum and to be part of it!
To keep a long story short: I've got a problem with an exercise from the subject 'forecasting' in my Logistics and Economics course. It has never been shown how to solve these kind of questions so it's very hard for me to understand the way of calculating.

The question
The needed time for picking a order at a DC is (No idea how to translate this but I think it is like: normal distributed) with a st. dev. of 25 minutes. If in 1,7% of all picks a full picking order take 3 hours or more then calculate the average time that is needed for picking a order.

127 minutes

I hope you can help me out to understand the way of calculating!


Ambassador to the humans
Could you tell me what value for a standard normal distribution is such that there is a probability of .017 that an observation will be above that value?