GARP 2011 Q.1

[Johnny Firpo]

Assume that a random variable follows a normal distribution with a mean of 50 and a standard deviation of 10. What percentage of this distribution is between 55 and 65?

Answer: 24,17%
(=0,9332-0,6915)

Actually, I don't get it with GARPs explanation...
How do we get the probabilities:
Prob (X < mean + 1,5*sd) - Prob (X < mean + 0,5*sd)?

 

[David Harper CFA FRM]

Hi Johnny Firpo see here @ http://forum.bionicturtle.com/threads/garp-sample-exam-1-level-1-question-1.4378/#post-11294