Graduate Management Admission Test (GMAT) Practice Test

In a speed problem where speeds are given but time or distance is missing, what is an effective strategy?

1. Assume time is 1 hour

2. Choose a distance that is divisible by the given speeds

3. Use average speeds to calculate distance

4. Ignore the speeds and guess a distance

The correct answer is: Choose a distance that is divisible by the given speeds

Choosing a distance that is divisible by the given speeds is an effective strategy in speed problems because it simplifies calculations and ensures that the results are manageable. When you're dealing with speed, distance, and time, the core relationship is encapsulated in the formula: \[ \text{Distance} = \text{Speed} \times \text{Time} \] By selecting a distance that can be evenly divided by the speeds involved, you avoid complications arising from fractions or decimals, which can lead to errors in calculation and interpretation. This approach allows you to directly relate time and speed to get coherent values. For instance, if you know the speeds are 30 mph and 60 mph, opting for a distance such as 60 miles means you can easily see that it takes 2 hours to travel at 30 mph (60 miles / 30 mph) and 1 hour at 60 mph (60 miles / 60 mph), allowing for straightforward comparisons of time and speeds. This method retains clarity in problem-solving and makes it easier to apply the principles of ratio and proportion, which are fundamental in many GMAT problems. Selecting distances in a manner that is mathematically convenient safeguards against miscalculations and enhances efficiency when analyzing speed-related questions.