Put pi on A next to 1 on B; find 7.92 on B and result is on A.
Put pi on B next to 1 on A; find 7.92 on A and result is on B.
Both times I get slightly less than 2.5. However, if I do it wrong and find 7.92 on the original scale, I get something that looks very close, slightly over 2.5, but is on the low end of the scale, telling me something's wrong. 3.14 * 7.92 should not be 2.x -- it should be 2x.x.
This is where slide rules will trip you up: decimal places. On the A and B scales for double decades, this is supposed to be less of a problem than the C and D scales. But it still takes practice.
(PS: 3.14 * 2.52 = 7.92, but 3.14 * 7.92 = 24.9) |
