Sure! Let's go through each of these problems step by step.
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Problem 1: For what value of \( a \) will \( 8 \times 10^3 \) be 40 times larger than \( a \times 10^2 \)?
We want: \[ 8 \times 10^3 = 40 \times (a \times 10^2) \] Simplifying gives: \[ 8 \times 10^3 = 40a \times 10^2 \] Dividing both sides by \( 10^2 \): \[ 8 \times 10 = 40a \] \[ 80 = 40a \] Solving for \( a \): \[ a = \frac{80}{40} = 2 \]
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Problem 2: What is 0.0000115741 in scientific notation?
This can be expressed as: \[ 1.15741 \times 10^{-5} \]
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Problem 3: What is \( 2.7 \times 10^7 \) in decimal notation?
This is: \[ 27,000,000 \text{ degrees Fahrenheit} \]
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Problem 4: Use scientific notation to determine which of these numbers has the least value: \( 98,789,000; 987,890,000; \) or \( 89,987,000 \).
- \( 98,789,000 = 9.8789 \times 10^7 \)
- \( 987,890,000 = 9.8789 \times 10^8 \)
- \( 89,987,000 = 8.9987 \times 10^7 \)
The least value is \( 8.9987 \times 10^7 \).
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Problem 5: Place the numbers in descending order.
- \( 2.3 \times 10^{-8} = 0.000000023 \)
- \( 2.3 \times 10^{-10} = 0.000000000023 \)
- \( 3.2 \times 10^{-10} = 0.000000000032 \)
- \( 2.3 \times 10^{-12} = 0.000000000000023 \)
In descending order:
- \( 2.3 \times 10^{-8} \)
- \( 3.2 \times 10^{-10} \)
- \( 2.3 \times 10^{-10} \)
- \( 2.3 \times 10^{-12} \)
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Problem 6: Which distance uses the most appropriate units?
- \( 3 \times 10^2 \) kilometers = 300 kilometers
- \( 3 \times 10^5 \) meters = 300,000 meters
- \( 3 \times 10^7 \) centimeters = 30,000,000 centimeters
- \( 3 \times 10^8 \) millimeters = 300,000,000 millimeters
The most appropriate unit for a distance would be kilometers, given that the other units express significantly larger values.
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Problem 7: What is the total number of acres in the park and the forest combined?
\[ 1.42 \times 10^6 + 1.2 \times 10^6 = (1.42 + 1.2) \times 10^6 = 2.62 \times 10^6 \text{ acres} \]
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Problem 8: What is the distance from Earth to the sun?
The distance from Venus to the sun is \( 6.7 \times 10^7 \) miles. The distance from Venus to the Earth is \( 2.6 \times 10^7 \).
Thus: \[ \text{Distance from Earth to the sun} = 6.7 \times 10^7 + 2.6 \times 10^7 = (6.7 + 2.6) \times 10^7 = 9.3 \times 10^7 \]
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Problem 9: Calculate \( 4.8 \times 10^{-3} - 9.4 \times 10^{-6} \).
Converting to scientific notation: \[ 4.8 \times 10^{-3} = 4.8 \times 10^{-3} \] Converting \( 9.4 \times 10^{-6} \): \[ 9.4 \times 10^{-6} = 0.0000094 \]
To perform the subtraction, convert \( 4.8 \times 10^{-3} \) to the same power: \[ 4.8 \times 10^{-3} = 4800 \times 10^{-6} \] Now subtract: \[ 4800 \times 10^{-6} - 9.4 \times 10^{-6} = (4800 - 9.4) \times 10^{-6} = 4790.6 \times 10^{-6} \] Converting back to scientific notation: \[ 4.7906 \times 10^{-3} \]
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Problem 10: How much heavier is a grain of rice than a strand of hair?
A strand of hair has mass \( 2.17 \times 10^{-5} \) ounces, and a grain of rice is \( 0.002 \) ounces, or \( 2 \times 10^{-3} \) ounces.
The difference is: \[ 2 \times 10^{-3} - 2.17 \times 10^{-5} \]
Converting \( 2 \times 10^{-3} \) into \( 10^{-5} \): \[ 2 \times 10^{-3} = 200 \times 10^{-5} \]
Thus: \[ 200 \times 10^{-5} - 2.17 \times 10^{-5} = (200 - 2.17) \times 10^{-5} = 197.83 \times 10^{-5} \]
In scientific notation: \[ 1.9783 \times 10^{-3} \]
If you need further assistance or clarifications, feel free to ask!