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------------------------------------------------ Select the correct answer.

A dust particle weighs [tex]$7.42 \times 10^{-10}$[/tex] kilograms. What is the weight of [tex]$5 \times 10^6$[/tex] dust particles represented in scientific notation?

A. [tex]$3.71 \times 10^{-4}$[/tex] kilograms
B. [tex]$3.71 \times 10^{-3}$[/tex] kilograms
C. [tex]$37.1 \times 10^{-3}$[/tex] kilograms
D. [tex]$37.1 \times 10^{-4}$[/tex] kilograms

Answer :

To find the weight of [tex]\(5 \times 10^6\)[/tex] dust particles, each weighing [tex]\(7.42 \times 10^{-10}\)[/tex] kilograms, you can follow these steps:

1. Identify the problem components:
- Each dust particle weighs [tex]\(7.42 \times 10^{-10}\)[/tex] kilograms.
- You need to find the total weight for [tex]\(5 \times 10^6\)[/tex] dust particles.

2. Set up the multiplication:
- Multiply the weight of a single particle by the number of particles:
[tex]\[
\text{Total weight} = (7.42 \times 10^{-10}) \times (5 \times 10^6)
\][/tex]

3. Multiply the coefficients:
- Multiply the numbers (7.42 and 5):
[tex]\[
7.42 \times 5 = 37.1
\][/tex]

4. Add the exponents of 10:
- Since you're multiplying powers of 10, add the exponents:
[tex]\[
10^{-10} \times 10^6 = 10^{-10 + 6} = 10^{-4}
\][/tex]

5. Combine the results:
- Combine the result from the coefficient multiplication with the power of ten:
[tex]\[
\text{Total weight} = 37.1 \times 10^{-4}
\][/tex]

6. Express in proper scientific notation:
- Scientific notation typically expresses the number with one non-zero digit before the decimal. So, [tex]\(37.1 \times 10^{-4}\)[/tex] can be adjusted to:
[tex]\[
3.71 \times 10^{-3}
\][/tex]

Therefore, the weight of [tex]\(5 \times 10^6\)[/tex] dust particles is [tex]\(3.71 \times 10^{-3}\)[/tex] kilograms. The correct answer is:

B. [tex]\(3.71 \times 10^{-3}\)[/tex] kilograms