High School

The distance from Earth to the Moon is about [tex]3.84 \times 10^5[/tex] kilometers. A piece of copy paper is about [tex]9.6 \times 10^{-8}[/tex] kilometers thick. About how many pieces of copy paper would need to be stacked to reach from Earth to the Moon?

A. [tex]4 \times 10^{12}[/tex]
B. [tex]25 \times 10^{13}[/tex]
C. [tex]4 \times 10^{13}[/tex]
D. [tex]2.5 \times 10^{14}[/tex]

Answer :

To solve the problem, we first determine how many sheets of copy paper, each with a thickness of [tex]$9.6 \times 10^{-8}$[/tex] kilometers, would be required to cover the distance to the Moon, which is approximately [tex]$3.84 \times 10^{5}$[/tex] kilometers.

Step 1: Write down the values

- Distance from Earth to the Moon:
[tex]$$ d = 3.84 \times 10^5 \text{ km} $$[/tex]
- Thickness of one piece of paper:
[tex]$$ t = 9.6 \times 10^{-8} \text{ km} $$[/tex]

Step 2: Set up the equation

We need to find the number of pieces, [tex]$N$[/tex], such that:
[tex]$$ N = \frac{d}{t} = \frac{3.84 \times 10^5}{9.6 \times 10^{-8}} $$[/tex]

Step 3: Divide the numbers

Perform the division by separating the numerical coefficients and the powers of 10:

1. Divide the coefficients:
[tex]$$ \frac{3.84}{9.6} = 0.4 $$[/tex]
2. Divide the powers of 10:
[tex]$$ \frac{10^5}{10^{-8}} = 10^{5 - (-8)} = 10^{13} $$[/tex]

Thus, the expression becomes:
[tex]$$ N = 0.4 \times 10^{13} $$[/tex]

Step 4: Express in standard scientific notation

Convert [tex]$0.4 \times 10^{13}$[/tex] to standard scientific notation:
[tex]$$ 0.4 \times 10^{13} = 4 \times 10^{12} $$[/tex]

Final Answer:

The number of pieces of copy paper required to reach from Earth to the Moon is:
[tex]$$ \boxed{4 \times 10^{12}} $$[/tex]

This corresponds to option A.