Canadian Forces Aptitude Test (CFAT) Practice

What is the next number in the series: -3, 9, -5, 25, -7, 49?

1. -7

2. -9

3. 9

4. 7

The correct answer is: -9

To determine the next number in the series, it's important to analyze the pattern of the sequence. We can break the series into two distinct alternating patterns: one for the negative numbers and one for the positive numbers. Starting with the negative numbers: -3, -5, -7. This part of the sequence is formed by subtracting 2 from the previous negative number. Following this pattern, the next logical number after -7 would be -9. Now let's look at the positive numbers: 9, 25, 49. This pattern appears to be the squares of consecutive odd numbers: - \(3^2 = 9\), - \(5^2 = 25\), - \(7^2 = 49\). Thus, the next number in this pattern would be the square of the next odd number, which is 9 (since \(9^2 = 81\)), but that number does not need to be determined to find the next term in the alternating sequence. Therefore, by focusing on the negative part of the sequence, the following number, based on the established pattern of subtracting 2 from the last negative term, is indeed -9.