Which of the following is the correct scientific notation for 0.0000000642?

• A. 6.42 × 10^{8}
• B. 6.42 × 10^{-7}
• C. 6.42 × 10^{-8}
• D. 0.642 × 10^{-7}

Answer: (C)

Verified step by step guidance

1. Identify the original number: 0.0000000642.
2. Count how many places the decimal point must move to the right to place it immediately after the first nonzero digit (6). This determines the exponent in scientific notation.
3. Since the decimal moves 8 places to the right, the exponent will be negative 8, indicating a small number less than 1.
4. Rewrite the number as a product of a number between 1 and 10 and 10 raised to the power of the exponent: \$6.42 \times 10^{-8}$.
5. Compare this form to the given options to confirm that \$6.42 \times 10^{-8}$ is the correct scientific notation.