Not having my CRP on me...
First up, get a rough estimate of the number you're expecting before touching the damn thing.
i.e. square route of 16. We're going to take a risk with 4 as our rough guess...
On the outer scale you'll need to locate the original number (16) and your rough guestimate, 4 (using 40 as the inner unit index is a 10... 40/10 = 4))
Put the inner unit index (the 10 in a black circle) on your rough estimate, 4, on the outer scale.
The original number, 16, should be opposite 4 (40 again) on the inner scale.
Obviously an easy example. For more complex numbers, home in with the rough guestimate and then slide the inner cirlce until the number opposite the inner unit index equals the number opposite the original number on the outer scale.
i.e. square route of 18.
guestimate 4
put the inner unit index on 4 (40 on the scale)
find 16 on the outer scale and you'll see that your guestimate on the inner scale is just past it.
Slide the inner scale back a touch until the number under the 16 is equal to the number opposite the inner unit marker.
Sorry for the lousy explanation! I find this method fastest in exams. Obviously spending a few nights messing around gets things a lot smoother...
I'll let someone else give you a better explanation now!
