Question 268 of 480
What is the result of simplifying the expression \( (2^3 \times 2^{-5}) \) and expressing it in standard form?
- \( 0.25 \)
- \( 0.5 \)
- \( 1 \)
- \( 4 \)
Correct Answer:
A
Explanation
To simplify the expression \( (2^3 \times 2^{-5}) \) and express it in standard form, let's break it down step-by-step.
### Step 1: Apply the Laws of Exponents
When multiplying numbers with the same base, we can use the law of exponents that states:
\[
a^m \times a^n = a^{m+n}
\]
In our case, the base is \( 2 \), and we have:
\[
2^3 \times 2^{-5}
\]
Using the law of exponents, we can combine the exponents:
\[
2^{3 + (-5)} = 2^{-2}
\]
### Step 2: Convert to Positive Exponent
The expression \( 2^{-2} \) can be rewritten using the property of negative exponents, which states:
\[
a^{-n} = \frac{1}{a^n}
\]
Thus, we have:
\[
2^{-2} = \frac{1}{2^2}
\]
### Step 3: Calculate \( 2^2 \)
Now, we need to calculate \( 2^2 \):
\[
2^2 = 4
\]
So, substituting back, we get:
\[
2^{-2} = \frac{1}{4}
\]
### Step 4: Express in Standard Form
The fraction \( \frac{1}{4} \) can also be expressed as a decimal:
\[
\frac{1}{4} = 0.25
\]
### Conclusion
Thus, the simplified expression \( (2^3 \times 2^{-5}) \) in standard form is:
\[
0.25
\]
### Answer
The correct option is **A. \( 0.25 \)**.
### Explanation of Other Options
- **B. \( 0.5 \)**: This option is incorrect because \( 0.5 \) is equivalent to \( \frac{1}{2} \), which does not match our result of \( \frac{1}{4} \).
- **C. \( 1 \)**: This option is incorrect because \( 1 \) would imply that the product of the exponents resulted in zero, which is not the case here.
- **D. \( 4 \)**: This option is incorrect because \( 4 \) is the result of \( 2^2 \), not \( 2^{-2} \).
### Common Pitfalls
- Forgetting to apply the laws of exponents correctly can lead to incorrect simplifications.
- Misinterpreting negative exponents can cause confusion; remember that a negative exponent indicates a reciprocal.
- Not converting fractions to decimals when required can lead to misinterpretation of the answer format.
### Revision Summary
- Use the law of exponents to combine terms with the same base.
- Convert negative exponents to positive by taking the reciprocal.
- Calculate powers accurately to avoid mistakes.
- Express final answers in the required format (standard form).