I see the image contains a list of numbers expressed in exponential notation. Let me review and verify the answers provided:

1. 21. $10 = 1.0 \times 10^1$ — Correct.
2. 22. $100 = 1.0 \times 10^2$ — Correct.
3. 23. $10,000 = 1.0 \times 10^4$ — Correct.
4. 24. $1,000,000 = 1.0 \times 10^6$ — Correct.
5. 25. $240 = 2.4 \times 10^2$ — Incorrect. The correct answer is $2.40 \times 10^2$, since you should use two decimal places.
6. 26. $2430 = 2.43 \times 10^3$ — Correct.
7. 27. $10,400 = 1.04 \times 10^4$ — Correct.
8. 28. $500 = 5.0 \times 10^2$ — Correct.
9. 29. $5600 = 5.6 \times 10^3$ — Correct.
10. 30. $1540 = 1.54 \times 10^3$ — Correct.

The only issue is with number 25, where the exponential form should include two decimal places (i.e., $2.40 \times 10^2$).

Would you like more details or have any further questions?

Here are 5 related questions you can explore:

1. How can we convert any given number into scientific notation?
2. Why is it important to use decimal places in scientific notation?
3. How does scientific notation simplify working with very large or very small numbers?
4. What is the difference between scientific notation and exponential notation?
5. How would you express 0.00056 in scientific notation?

Tip: Always use the correct number of significant figures when converting numbers into scientific notation to avoid rounding errors.