Question

Which set of numbers is arranged in descending order?
A. 7 × 10^−30, 7.2 × 10^−25, 7.2 × 10^−30, 7.6 × 10^−25
B. 7.6 × 10^−25, 7.2 × 10^−30, 7.2 × 10^−25, 7 × 10^−30
C. 7.2 × 10^−30, 7 × 10^−30, 7.6 × 10^−25, 7.2 × 10^−25
D.7.6 × 10^−25, 7.2 × 10^−25, 7.2 × 10^−30, 7 × 10^−30

Answer 1

To arrange the numbers in descending order, we first need to convert them to a common notation or understand their values, especially with their powers of ten. Let's analyze each option:

1. **A.**
- \(7 \times 10^{-30}\)
- \(7.2 \times 10^{-25}\)
- \(7.2 \times 10^{-30}\)
- \(7.6 \times 10^{-25}\)

Comparing powers of ten:
- \(7.2 \times 10^{-25} > 7.6 \times 10^{-25} > 7.2 \times 10^{-30} > 7 \times 10^{-30}\)
This is not in descending order.

2. **B.**
- \(7.6 \times 10^{-25}\)
- \(7.2 \times 10^{-30}\)
- \(7.2 \times 10^{-25}\)
- \(7 \times 10^{-30}\)

This option places \(7.2 \times 10^{-30}\) incorrectly in sequence, as it is less than \(7.2 \times 10^{-25}\). This is not in order.

3. **C.**
- \(7.2 \times 10^{-30}\)
- \(7 \times 10^{-30}\)
- \(7.6 \times 10^{-25}\)
- \(7.2 \times 10^{-25} \)

This option has the first two terms in the incorrect order (they should be at the end), so it is not in descending order.

4. **D.**
- \(7.6 \times 10^{-25}\)
- \(7.2 \times 10^{-25}\)
- \(7.2 \times 10^{-30}\)
- \(7 \times 10^{-30}\)

This option correctly places \(7.6 \times 10^{-25} > 7.2 \times 10^{-25} > 7.2 \times 10^{-30} > 7 \times 10^{-30}\).

Thus, option **D** is arranged in descending order.