Creating an exponential equation

In summary, the conversation discusses the doubling of a bacteria culture starting with 3000 bacteria and reaching 48000 after 3 hours. The doubling period is calculated using the half-life formula and is found to be 3/4 hours, which is correct despite the negative sign.
  • #1
TN17
47
0

Homework Statement



A bacteria culture starts with 3000 bacteria.
After 3 h, the estimated counting is 48 000. What is the doubling period?


The Attempt at a Solution


I figured it would look like the half-life formula, so I wrote it as:

B = B0(0.5)t/h
Then I subbed numbers in:
48 000 = 3000(0.5)3/h
16 = 3/h (log0.5)
h = 3 (log0.5/log16)
h = -0.75

The answer at the back was 3/4 h, but I don't know if I did it correctly. I don't think the (-) makes sense.
 
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  • #2
Replace 0.5 with 2... i.e replace "half life" with "doubling".
 
  • #3
Coto is exactly right. Note, by the way, that 48000 is 16 times 3000 so in 3 hours it has far more than doubled- the doubling time is less than 3 hours not more.

Which means, in fact, that you answer is correct- it has doubled 4 times in 3 hours. The doubling time is 3/4 hours. You have a negative sign because
[tex]\left(\frac{1}{2}\right)^{-1}= 2[/tex]
 
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1. What is an exponential equation?

An exponential equation is a mathematical expression that involves a base raised to a variable exponent. The base is usually a constant number, while the exponent is a variable that can take on different values. The value of an exponential equation increases or decreases rapidly as the exponent increases or decreases.

2. How do you create an exponential equation?

To create an exponential equation, you need to first determine the base and the exponent. Then, you can write the equation in the form y = ab^x, where a is the initial value and b is the base. You can also use the formula y = ae^(kx) for continuous growth or decay, where a is the initial value and k is the constant rate of change.

3. What are some real-world applications of exponential equations?

Exponential equations are commonly used to model situations with exponential growth or decay, such as population growth, compound interest, and radioactive decay. They can also be used in fields like physics, biology, and finance to describe natural phenomena or predict future trends.

4. How do you solve an exponential equation?

To solve an exponential equation, you can use logarithms or exponent rules. If the equation is in the form y = ab^x, you can take the logarithm of both sides to isolate the variable. If the equation is in the form y = ae^(kx), you can use exponent rules to simplify the equation and then solve for the variable.

5. What are some common mistakes to avoid when creating an exponential equation?

Some common mistakes to avoid when creating an exponential equation include using the wrong base or exponent, forgetting to include the initial value, and using the wrong formula for continuous growth or decay. It is also important to make sure that the units for the base and exponent are consistent and that the equation accurately reflects the real-world situation.

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