GMAT® Average Speed Problems: The Rate Chart and the Formula That Solve Them
If you've ever averaged two speeds on an average speed question, that makes total sense.
That's how most of us would do it in real life.
But on the GMAT®, that move is usually a trap.
You see two speeds — say 30 mph and 60 mph — and you average them. You get 45 mph. It seems right. It feels right.
And on most GMAT® average speed setups, it will send you to the wrong answer.
The reason is subtle but important. If someone travels at 30 mph for part of a trip and 60 mph for the rest, they spend more time traveling at the slower speed. So the actual average speed is pulled closer to 30 than to 60. The simple average of the two rates does not account for that.
Once you see why, the fix is straightforward. And it starts with a formula.
We walked through three real average speed problems in Episode 47 of Real GMAT® Problems, our podcast series. Here is the framework they all share — and the rate chart setup that keeps the algebra organized.
The Formula
Average speed = total distance / total time.
If you memorize one thing for these problems, make it that.
A helpful default is to write it at the top of your scratch work any time the question is about average speed.
It may seem too simple to matter, but writing it out does two things. First, it reminds you that you need total distance and total time — not just the individual speeds. Second, it acts as a defense against the averaging trap we just described.
We have seen hundreds of students improve their accuracy on rates problems just by adding this one habit. Five seconds of writing. Significant difference in results.
The Rate Chart
The formula tells you what to solve for. The rate chart helps you organize the information so you can do it.
Here is how it works.
Write "Rate × Time = Distance" across the top. Below that, create one row for each leg of the journey. If the problem gives you an average speed for the whole trip, add a "Total" row at the bottom.
Then fill in whatever the problem gives you. Distances go in the distance column. Speeds go in the rate column. Times go in the time column. Leave blanks where you do not have information yet.
From there, you use Rate × Time = Distance to solve for the missing values. Usually that means dividing distance by rate to get time, or dividing distance by time to get rate.
The chart does not do anything you could not do without it. But it keeps all the moving parts visible. On easier problems, that may feel unnecessary. On harder problems — where you have variables instead of numbers, or where the algebra involves fractions with uncommon denominators — it is the difference between staying organized and getting lost.
For most people, it's worth using the chart on almost every rates problem, even the easy ones. The habit is easy to maintain when the problem is simple, and it pays off when the problem is not.
What "Along the Same Route" Means
A phrase that appears frequently in average speed problems: "along the same route."
It means the distances for each leg of the trip are equal. You may not know what that distance is. That is fine. Assign a variable — D, for example — and write it in both rows of the chart.
This may sound obvious if you have been studying for a while. If you are just getting started, it can be easy to miss. The key is recognizing that the phrase is giving you a piece of information: the distances are the same. Write that down and you are in a stronger position.
Taking Leaps of Faith
On more complex problems, you will not always see the full solution path from the start. The chart may have two variables and one equation. The algebra may look messy. You may not be sure the approach you are taking will lead anywhere.
That is normal.
If the chart is set up correctly and the formula is written down, you have enough reason to keep going. Solve for what you can. See what simplifies. Variables may cancel. Fractions may reduce. The path forward often only becomes clear after you take the next step.
This is a broader GMAT® skill, not just a rates skill. The problems are designed to test reasoning — which includes the ability to proceed with partial confidence and adjust as you go. A good setup gives you the foundation to do that.
The Three Problems
We covered three average speed problems from the 11th edition of the Official Guide for GMAT® Review, each building on the last.
Problem 1 (warm-up): Car X and Car Y traveled the same 80-mile route. One speed given directly, the other is 50% faster. Straightforward application of the formula and the chart.
Problem 2 (medium): Jill went up a hill at an unknown constant speed. Two unknowns, an "along the same route" setup, and an average speed for the round trip. The chart needs a total row and the algebra involves adding fractions with variable denominators.
Problem 3 (hard): During a trip on an expressway, Don drove X miles. A four-row chart, algebra with two variables, and a percent change layer as the final step.
Each worked solution walks through the full rate chart setup and the algebra step by step.
What to Take Away
Two takeaways to keep on your scratch pad:
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Write "average speed = total distance / total time" at the top any time the question is about average speed.
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Set up the rate chart before doing any math. One row per leg. A total row when needed. Fill in what you have. Solve for what you do not.
Those two habits handle the setup for most distance and speed questions the GMAT® will give you. The algebra varies, but the framework stays the same.
If you want more practice with the rate chart, we also have an episode on work and rate problems (Episode 44 of our podcast series), which uses the same organizational structure for a different type of question.
FAQ
Is average speed ever the simple average of two speeds?
Usually not on the GMAT®. The simple average only works when the traveler spends equal amounts of TIME at each speed — not equal distances. Since many problems involve equal distances at different speeds, the simple average will point you the wrong way.
When should I add a "Total" row to the rate chart?
Any time the problem gives you an average speed for the entire trip or asks you to compare total times across different scenarios. The total row captures the relationship between total distance and total time, which is usually what the problem is testing.
What if I have two variables and one equation?
Keep going. In many average speed problems, the variables cancel during the algebra. This is by design — the problem gives you enough information to solve, even when it does not look like it at first. This is a common place for the "leap of faith."
How do I handle percent change on a rates problem?
Use the formula: (new value − old value) / old value × 100. If the problem says "percent greater than," the value after "than" is the old value. We cover this in detail in Problem 3.
Is the rate chart the same as a rate/work table?
Yes. The structure is identical — Rate × Time = Distance for speed problems, Rate × Time = Work for work/rate problems. If you learn the chart for one type, you can use it for the other.
More practice:
- Episode: Episode 47 of Real GMAT® Problems
- Worked solutions: Problem 1 (Car X and Car Y), Problem 2 (Jill), Problem 3 (Don)