How to use slide rules

Multiplication

To multiply two small numbers, 2x3

- Use rules C and D.  Starting from the left, line up C (1) to D (2).  
- Move cursor to C (3).  D (6) shows the answer.

To mulitply two big numbers, 6x7

- Use rules C and D.  Starting from the right, line up C (1) to D (6).
- Move cursor to C (7).  D (4.2) shows the answer.  Adjust by 10 = 42.

To multiple two big numbers, 12 x 67

- Use rules C and D.  Starting from the left, line up C (1.2) to D (1.2).
- Move cursor to C (6.7).  D (8) shows the answer.  Adjust by 
  thinking 10x70=700.  So 8 must be 800.

What are the limits of rules C and D?

- Reading C and D from left to right is only for small digits, like 2x4.
- Reading C and D from right to left works for bigger digits.

Division

To divide two small numbers, 4.5 / 7.8

- Use rules C and D. 
- Move cursor to D (4.5).
- Move C (7.8) until 7.8 hits the cursor.
- Move cursor to C (1).
- The answer is in D (5.78).
- Since 4/8 ~ 0.5, the answer is 0.578.

To divide two numbers, 142 / 83

- Use rules C and D.
- Move cursor to D (1.42).
- Move C (8.3) until 8.3 hits the cursor.
- Move cursor to C (1).
- The answer is in D (1.72).
- Since 160/80 ~ 2, the answer is 1.72.

To divide two big numbers, 2,313,184 / 80,234

- Use rules C and D.
- 2,313,184 ~ 2.3e6.
- 80,234 ~ 8.0e4.
- Move cursor to D (2.3).
- Move C (8.0) until 8.0 hits the cursor.
- Move cursor to C (1).
- The answer is in D (2.88).
~ Adjusted for scale, 2.88e2 ~ 28.8.

Sin 30

- Use rule A and S.  Align rules.
- Move cursor to S (30).
- The answer is in A (5).
- Adjusted, the answer is 0.5.

Cos 30

- Once you can do sin 0-90, you can do any sin or cos.
- If you look at the cos/sin charts, cos 30 is the same as sin 60.
- Sin 60 = 0.866.

Tan 30

- Use rule D and T.  Align rules.
- Move cursor to T (30).
- The answer is in D (5.76).
- Adjusted, the answer is 0.576.