To find out how many pennies are in a pile that weighs \( 3.596 \times 10^4 \) lb, we can use the formula:
\[ \text{Number of pennies} = \frac{\text{Total weight of pennies}}{\text{Weight of one penny}} \]
Plugging in the values:
\[ \text{Number of pennies} = \frac{3.596 \times 10^4 \text{ lb}}{5.8 \times 10^{-3} \text{ lb/penny}} \]
Now, we perform the division:
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Divide the coefficients: \[ \frac{3.596}{5.8} \approx 0.62068966 \approx 0.62 , (\text{rounded to two decimal places}) \]
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Subtract the exponents: \[ 10^{4 - (-3)} = 10^{4 + 3} = 10^{7} \]
Combining these, we get: \[ \text{Number of pennies} \approx 0.62 \times 10^{7} \]
To express \( 0.62 \times 10^{7} \) in standard scientific notation, we move the decimal point one place to the right, which increases the exponent by 1:
\[ 0.62 \times 10^{7} = 6.2 \times 10^{6} \]
Thus, the final answer is:
\[ \boxed{6.2 \times 10^6} \]