Statistics linear transformation rescale

[bcahmel]

Homework Statement

Mean of 25 and standard deviation of 5. Rescale the test using linear transformation so that the mean is 100?
and the standard deviation is 20...

Homework Equations

xnew=a+bx

The Attempt at a Solution

I don't know...15+4x? I really don't understand how to calculate this. I read my book and its useless! Any help? :)

 

[HallsofIvy]

Where did you get the "15"? 4(25)= 100 and 4(5)= 20. Looks to me like you just want to multiply by 4.

"I read my book and it is useless"
Then you can do nothing to improve the situation.

"I have trouble understanding my book"
Then you can work on reading the book more carefully and improve the situation.

Which do you prefer?

 

[bcahmel]

well the first one is true but I'd prefer the second one.