Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.
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Transcript of Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.
![Page 1: Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dbf5503460f94ab2bf7/html5/thumbnails/1.jpg)
Do this (without a calculator!)
42.5 x 37.6
![Page 2: Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dbf5503460f94ab2bf7/html5/thumbnails/2.jpg)
A blast from the past
Slide Rules
![Page 3: Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dbf5503460f94ab2bf7/html5/thumbnails/3.jpg)
![Page 4: Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dbf5503460f94ab2bf7/html5/thumbnails/4.jpg)
![Page 5: Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dbf5503460f94ab2bf7/html5/thumbnails/5.jpg)
Logarithms were invented by the Scottish mathematician and theologian John Napier and first published in 1614. He was looking for a way of quickly solving multiplication and division problems using the much faster methods of addition and subtraction. Napier's way of doing this was to invent a group of "artificial" numbers as a
direct substitute for real ones.
![Page 6: Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dbf5503460f94ab2bf7/html5/thumbnails/6.jpg)
He called this numbering system logarithms (which is Greek for "ratio-number", apparently). Logarithms are consistent, related values which substitute for real numbers. Incidentally, it wasn't until a few years later, in 1617, that a fellow mathematician named Henry Briggs adapted Napier's original "natural" logs to the more commonly used and convenient base 10 format.
![Page 7: Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dbf5503460f94ab2bf7/html5/thumbnails/7.jpg)
To see how these are useful for multiplication, consider what happens if you want to multiply 10 x 1,000, as a simple example. The secret here is that you could just add their logs together and then take the anti-log of the result.
Why? Because log xy =
Source: http://www.sliderule.ca/intro.htm
![Page 8: Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dbf5503460f94ab2bf7/html5/thumbnails/8.jpg)
![Page 9: Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dbf5503460f94ab2bf7/html5/thumbnails/9.jpg)
How do logs help in multiplication?
2 x 3 = yLog (2 x 3) = log y
Log 2 + log 3 = log y.301 + .477 = log y
.778 = log y10.778 = y
y = 6
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To find log x:1. Line up cursor with x on D scale2. Read number on L scale3. Add “1” to your answer for each
number past the ones place
Ex. Find log 25Line up cursor with 2.5 on D scaleRead number on L scaleBecause there’s a number in the 10’s spot,
add 1.
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Use the slide rule to find the following logs.
1. Log 32. Log 83. Log 1.24. Log 385. Log 526. Log 135
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What number has a log of. . .
1. 0.62. 1.373. 2.2
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To multiply (xy):1. Line up "1" of C scale with x
on D scale2. Set hairline of cursor over y on
C scale.3. Answer is number on D scale
Ex. Multiply 2x3:Line up "1" on C scale with 2 on D-scaleMove cursor to 3 on C scaleRead # on D scale
![Page 14: Do this (without a calculator!) 42.5 x 37.6. A blast from the past Slide Rules.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dbf5503460f94ab2bf7/html5/thumbnails/14.jpg)
Do these:1. 15 x 42. 18 x 3.73. 1.5 x 2.34. 280 x 0.345. .0215 x 3.54
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To divide ( x ÷ y ):1. Line up x on D scale with y on
C scale.2. Answer lines up with “1” on D
scale.
Ex. Divide 8 ÷ 43. Line up 8 on D scale with 4 on C scale4. Move cursor to 1 on C scale5. Read # on D scale
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Do these:1.15 ÷ 32.62.4 ÷ .7073.23 ÷ 1.64.0.53 ÷ 7
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Combining Operations 1. Think of problem as 2. Line up x on D scale with z on
C scale3. Move cursor to y on C scale4. Read answer on D scale
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Do these: 1.
2.
3.
4.