To find how many pennies are in a pile that weighs \( 3.596 \times 10^4 \) lb, you can divide the total weight of the pile by the weight of a single penny.
- Weight of one penny: \( 5.8 \times 10^{-3} \) lb
- Total weight of the pile: \( 3.596 \times 10^4 \) lb
Now, perform the division:
\[ \text{Number of pennies} = \frac{\text{Total weight}}{\text{Weight of one penny}} = \frac{3.596 \times 10^4 \text{ lb}}{5.8 \times 10^{-3} \text{ lb}} \]
To simplify that calculation:
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Divide the coefficients: \[ \frac{3.596}{5.8} \approx 0.620 \]
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Subtract the exponents in the powers of ten: \[ 10^{4 - (-3)} = 10^{4 + 3} = 10^{7} \]
So, combining the results, we have: \[ \text{Number of pennies} = 0.620 \times 10^7 \]
In scientific notation: \[ 6.2 \times 10^6 \]
Therefore, the correct answer is: \[ \boxed{6.2 \times 10^6} \]