As you will see, these two questions involve completely different skills. Example 1 is a problem solving type question involving the application of Maths skills (e.g. you could create an algebraic expression and use that to help you solve it, or substitute the answers to see which one fits the question). You might find you could work through example 1 quite quickly and use up much less than the 1 minute 48 seconds mentioned above. Or, on the other hand, you may take longer depending on your experience of this type of problem. Example 2 is certainly going to take a bit longer to read and understand due to the amount of information it contains. Also, because you are given an extra piece of information in the question, this may also take longer to comprehend.
The point here is that each question is going to inevitably take a slightly different length of time to answer depending on your familiarisation with the question-type, and whether it is a problem solving type question or a critical thinking type question.
Therefore, a more efficient way of managing your time might be to know how long you have available per 5 or even 10 questions: