How did you go?  Did you get the answer 7.5?  If you did, give yourself a pat on the back, you're well on the way to become a slide rule guru!  If not, perhaps you rushed thing a little bit, so go back and check your steps carefully.  If you're really not sure read the explanation below.

Let's go through our steps ...

1. We line up the left index (C1) with the first number 2.5 (on the D scale).
2. Slide the cursor to the second number, 3 on the C scale.
3. Now read the answer below the 3 and you find 7.5 (on the D scale).

 Are you ready?  If you are click here to go back to the lesson.