Math Reasonings Solved Exercises
A car travels at 10 miles per hour (mph) for one hour, doubles its speed in the second hour, and continues doubling its speed every hour thereafter. If the vehicle keeps this rate of change, what speed will it be traveling at during the seventh hour?
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3200 mph
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1280 mph
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640 mph
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320 mph
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256 mph
Try to solve it before checking the answer.
640 mph
1st hour: 10 mph
2nd hour: \(10 \times 2 = 20 \) mph
3rd hour: \(
(10 \times 2) \times 2 = 10 \times 2^2 \) mph
4th hour: \(
(10 \times 2^2) \times 2 = 10 \times 2^3 \) mph
…
7th hour: \(
10 \times 2^6
\, \frac{Km}{h}
= \boldsymbol{640} \) mph