Calculating general normal random probability

[Biochemgirl2002]

Homework Statement

Suppose X ~ N(20, 25). Determine the following
probabilities.
(A) P(X < 18)
(B) P(X > 27)
(C) P(13 < X < 23)

Relevant Equations

if X~N(mean, standard deviation squared) then,
z=(x-mean)/(standard deviation)~N(0,1)

a) P(X<18) = (18-20)/sqrt25
=-2/5
=-0.4
then you use the standard normal table and find that;
P(X<18)=0.3446

b) P(X>27)
= (27-20)/5
= 7/5
= 1.4

P(Z>1.4)
=P(Z<-1.4)
=0.0808

C) =(13<X<23)
=13-20/5 , 23-20/5
=-7/5 , 3/5
=-1.4 , 0.6

P(Z<0.6)-P(Z<-1.4)
=0.7257-0.0808
=0.6449

 

[WWGD]

Sorry, what is your question? Do you want us to double-check your work?

 

[Biochemgirl2002]

Sorry, what is your question? Do you want us to double-check your work?

Yes, sorry. I am not sure that i have done the right steps.
Mainly my issue is because the question says X~N(20,25) and i am not sure if i am to assume that the mean is 20 and the standard deviation squared is 25.
as well, my other concern is that the equation isn't the standard deviation squared, so as you can see in my results, i square rooted the 25 so that it is only 5 which i believe makes sense.

thank you for your time!