Chapter 13: Problem 14
Use logarithms to the base 10 to find the indicated logarithms. $$\log _{100} 3720$$
Short Answer
Expert verified
Using the base 10 logarithm, \( \log_{100} 3720 \approx 1.7851 \).
Step by step solution
01
Change of Base Formula
To find a logarithm with a base other than 10, we can use the change of base formula. The change of base formula is given by:\[ \log_b a = \frac{\log_c a}{\log_c b} \]In this exercise, we are asked to find \( \log_{100} 3720 \), and we will use base 10 for our calculations. Thus, the expression becomes:\[ \log_{100} 3720 = \frac{\log_{10} 3720}{\log_{10} 100} \]
02
Calculate \(\log_{10} 100\)
Next, we need to calculate \( \log_{10} 100 \). We know that 100 can be written as \(10^2\). Therefore:\[ \log_{10} 100 = \log_{10} (10^2) = 2 \times \log_{10} 10 = 2 \times 1 = 2 \]
03
Calculate \( \log_{10} 3720 \)
Now, let's approximate \( \log_{10} 3720 \) using a scientific calculator. The result is approximately:\[ \log_{10} 3720 \approx 3.5702 \]
04
Apply the Change of Base Result
Now use the results from Steps 2 and 3 to find \( \log_{100} 3720 \) as follows:\[ \log_{100} 3720 = \frac{\log_{10} 3720}{\log_{10} 100} = \frac{3.5702}{2} \approx 1.7851 \]
05
Round the Answer
For final presentation, it's often helpful to round the answer to a certain number of decimal places to simplify communication. Therefore, rounding 1.7851 to 4 decimal places, we get approximately:\[ \log_{100} 3720 \approx 1.7851 \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Change of Base Formula
When dealing with logarithms that don't have a base of 10, you can employ a neat trick called the Change of Base Formula. This formula is a lifesaver when your calculator only likes base 10 (common logarithms) or base e (natural logarithms). The formula goes like this:
- Take the logarithm of your number using a preferred base, like 10.
- Divide it by the logarithm of the original base, still using your preferred base.
Base 10 Logarithms
Base 10 logarithms, often referred to as common logarithms, are a favorite among mathematicians and students alike because they link directly to our decimal system. They are denoted by \( \log_{10} \) or sometimes just \( \log \).One of the neat properties of any base 10 logarithm is what happens with powers of 10:
- \( \log_{10} 10 = 1 \)
- \( \log_{10} 100 = 2 \)
- \( \log_{10} 1000 = 3 \)
Scientific Calculator Usage
A scientific calculator can be your best friend when dealing with logarithmic calculations, especially when you need to calculate logarithms to several decimal places. When using a scientific calculator:
- Find the "log" button – it's for base 10 logs.
- Enter the value you need the logarithm of, typically by typing the number first and then pressing the "log" button.
- Read the result carefully; it may be a long decimal.
Rounding Decimals
Rounding decimals is an essential skill for presenting your calculations in a clear and comprehensible manner. It helps to simplify long decimal numbers where excessive precision isn't necessary:
- Identify how many decimal places are needed to express your result. Often, 4 places are sufficient for most school tasks.
- Look at the number in the next decimal place to decide whether to round up or down – if it's 5 or more, round up.
- Remember, rounding keeps your answer tidy and reader-friendly.