In each of the number-pairs, the second number is obtained by performing a certain mathematical operation on the first number. Three of the following pairs follow the same pattern and thus form a group. Select the number-pair that does NOT belong to that group.

Solution

Let's analyze each pair: 1. 22, 34 To obtain the second number, we can see that 22 * 1.5 = 33, and adding 1 to it gives 34. 2. 11, 12 To obtain the second number, it seems like we're adding 1 to the first number. 3. 25, 42 To obtain the second number, we can see that 25 * 1.5 = 37.5, and rounding up to the nearest integer gives 38. However, this doesn't match with 42. 4. 17, 24 To obtain the second number, we can see that 17 * 1.5 = 25.5, and rounding up to the nearest integer gives 26, which is not equal to 24. Option 3 is the odd one out because the pattern for obtaining the second number does not follow a consistent rule. So, the correct answer is 3. 25, 42.