Speed problems: The Speed Table - Handling Speed Problems with Data Overload
Correct.
Incorrect.
Incorrect.
If you feel confused by all the details in this problem, don't blame yourself. The writers of this problem try to confuse. However, you can tackle this complication, if you organize the data in the "speed table":
Gustav ran 32 meters uphill at a constant speed, then he ran 36 meters downhill at a faster constant speed, so that his downhill speed was faster by 2 meters per second than his uphill speed. Running uphill took Gustav 2 seconds more than running downhill. Gustav's speed running downhill was how many meters per second?
|
speed | time | distance | |
|---|---|---|---|
| Up |
v | t+2 |
32 |
| Down |
v+2 | t |
36 |
Assign each of the values in the question to the appropriate cell in the table.
Use a new row whenever there is more than one journey, more than one traveler, or more than one segment of the road. A new segment is determined by a change in conditions, usually a change of speed. Here, for example, the speed changes between the way up and the way down. In the table above you can see the relevant excerpts next to each row.
Highlight the value you are asked about - In this case it is the downhill speed (in the table above it is highlighted in red. In the GMAT where you only have a black marker, you'll just circle the relevant cell).
What are you going to do now?
Incorrect.
This is definitely not the most efficient way to solve the problem.
Way to go!
Let's summarize: Use the table to organize!
1. Fill the table: Assign each of the values in the question to the appropriate cell in the table. Use a new row whenever there is more than one journey, more than one traveler or more than one segment.
2. Highlight the value you are asked about
3. Plug in the answer choices until one of them fits in with all the data in the table.
Don't be tempted to solve equations. There is a faster, better option: Plugging In the Answers. Pick up the answer choices one by one and plug them into v+2. Eliminate (POE) the ones that do not fit the rest of the data.
|
speed | time | distance | |
|---|---|---|---|
| Up |
v | t+2 |
32 |
| Down |
v+2 | t |
36 |
Start with answer choice A: v+2=2. Well, that means that v=0, which is absurd. Eliminate this choice.
Go on to answer choice B: v+2=3. This means that t=36/3=12 seconds. Now check whether these values also fit the first row, which now reads Speed=v=1, Time=(12+2), Distance=32. Clearly, the values don't fit the first row. POE B and go on to C.
When you check answer choice D, everything fits in: v+2=6. This means that v=4 meters per second, and that t=36/6=6 seconds. In the first row the Speed=v=4, Time=t+2=8, and the Distance is 4×8=32 indeed. The correct answer is D.
Each row can be translated into an equation according to speed×time=distance. There are two equations and two unknown variables, t and v. I am ready to solve them!
I'd prefer to plug the answer choices into the table (i.e., into v+2) and eliminate the ones that don't fit in the table.
