C and D Scales
Definition

  The C, on the sliding rule, and D, on a fixed rule, scales

Multiplication
  To multiply put the C index over the first multiplicand on D, put the cursor over the second multiplicand on C.  The product is the cursor location on D.  Let's multiply 1.75 by 4.5.

Slide C|1 to D|1.75 ,
Slide Cursor to C|4.5 ,
D|Cursor is the product.
It looks like 7.88 to me. The actual product, at four digits, is 7.875. Close enough! If you think it is 7.87 to 7.89
Popup interguesspulate window.

 

  What happens if the product is greater than ten?  Then we "wrap around" by using the right index on the C scale.  10ft 3.04, 15ft 4.48

Slide C|1 to D|3.04.   Look at the location of C|4.48.   It is past D|10.  Put cursor at D|3.04, this marks the spot so we don't have to decide exactly where D|3.04 is a second time.  To "wrap", slide C|10 right to the cursor at D|3.04.   When doing this C1 becomes value 10 and C10 value 100.  Move the cursor to C|4.48


that same spot. C|10 is under the cursor.  By putting the cursor at D|3.04 first,.  For the result move the cursor to C|4.48, read the product under the cursor on D as 1.36 times 10 because we wrapped, or 13.6. (13.6192)

Move Slide
Move Cursor

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Copyright © 2004, Dale Yarker