The hard way:

• Cursor to left index of D
• Slide to 4 on C at cursor

The easy way:

• Cursor to 4 on C
• The CI scale is the inverse, or reciprocal, of the C scale.
• The DI scale is the inverse of the D scale.
• CIF is the inverse of CF.

Note that C and CI, D and DI, and CF and CIF run in opposite directions, so that every number on each is the inverse of the corresponding number on the other.

Another easy method for finding reciprocals:

Find: reciprocal of 4

• Slide right index of C to 4 on D
• Or place left index of C at 4 on D