To evaluate the expression 18.39×3.8248.63×8.83 using logarithm tables, we will follow these steps:
Let X=18.39×3.8248.63×8.83.
Taking the logarithm of both sides:
logX=log(48.63×8.83)−log(18.39×3.82)
Using the logarithm properties log(ab)=loga+logb and log(ba)=loga−logb:
logX=(log48.63+log8.83)−(log18.39+log3.82)
Step 1: Find the logarithms of each number using a 4-figure logarithm table.
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For 48.63:
- Characteristic: There are 2 digits before the decimal point, so the characteristic is 2−1=1.
- Mantissa: Look up 48 under 6, which is 6866. The mean difference for 3 is 3. So, 6866+3=6869.
- log48.63=1.6869
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For 8.83:
- Characteristic: There is 1 digit before the decimal point, so the characteristic is 1−1=0.
- Mantissa: Look up 88 under 3, which is 9450.
- log8.83=0.9450
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For 18.39:
- Characteristic: There are 2 digits before the decimal point, so the characteristic is 2−1=1.
- Mantissa: Look up 18 under 3, which is 2625. The mean difference for 9 is 21. So, 2625+21=2646.
- log18.39=1.2646
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For 3.82:
- Characteristic: There is 1 digit before the decimal point, so the characteristic is 1−1=0.
- Mantissa: Look up 38 under 2, which is 5821.
- log3.82=0.5821
Step 2: Substitute the logarithm values into the equation for logX.
logX=(1.6869+0.9450)−(1.2646+0.5821)
Step 3: Perform the additions.
- Numerator sum: 1.6869+0.9450=2.6319
- Denominator sum: 1.2646+0.5821=1.8467
Step 4: Perform the subtraction.
logX=2.6319−1.8467
logX=0.7852
Step 5: Find the antilog of 0.7852.
- Mantissa: Look for 78 under 5 in the antilog table, which is 6095. The mean difference for 2 is 3. So, 6095+3=6098.
- Characteristic: The characteristic is 0. This means there is 0+1=1 digit before the decimal point.
- Antilog 0.7852=6.098
Therefore, X≈6.098.
18.39×3.8248.63×8.83≈6.098
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