Speed problems: The Speed Table - Handling Speed Problems with Data Overload
Jason drives to his parents' house and back home the same way. On the way to his parents' house, his speed is 10 kilometers per hour slower than his speed on his way back, and therefore it takes him 20 minutes longer. If Jason drives to his parents' house at 50 kilometers per hour, how many minutes does he spend on his way back from his parents' house?
Answer choice C, $$\color{red}{t = 100 \text{ minutes} =1\frac{2}{3} \text{ hours}}$$, is the only answer that fits both rows of the table.
| | SPEED (KM/H) | TIME (H) | DISTANCE (KM) |
|-------------|--------------|----------------------------------|---------------|
| To parents' | $$50$$ | $$2$$ | $$50 \times 2 = 100$$ |
| Back home | $$60$$ | $$\color{red}{1\frac{2}{3}}$$ | $$60 \times 1\frac{2}{3} = 100$$ |
Since the distance is 100 km for both trips, this is the correct answer.
Incorrect.
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Incorrect.
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Incorrect.
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Incorrect.
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Correct.
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Since Jason takes the same route on both trips, the distances must be equal.
This is what the table looks like:
| | SPEED (KM/H) | TIME (H) | DISTANCE (KM) |
|-------------|--------------|----------------------------------|---------------|
| To parents' | $$50$$ | $$t+\color{green}{\frac{1}{3}}$$ | $$s$$ |
| Back home | $$60$$ | $$\color{red}{t}$$ | $$s$$ |
Pay attention to the units. The answer choices are in minutes, and you have to convert them into hours before you plug them in so that they fit the speed unit presented in the question. The {color:dark-green}20 minute{/color} difference between the two ways is also converted to {color:dark-green}$$\frac{1}{3}$$ hour{/color}.
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