Problem 11 · 2023 AMC 8
Medium
Ratios, Rates & Proportions
distance-speed-timeestimate-and-pick
NASA's Perseverance Rover was launched on July 30, 2020. After traveling 292,526,838 miles, it landed on Mars in Jezero Crater about 6.5 months later. Which of the following is closest to the Rover's average interplanetary speed in miles per hour?
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Answer: C — About 60,000 mph.
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Hint 1 of 2
The answer choices jump by factors of 10, not by small amounts — that's permission to round wildly. Don't touch 292,526,838; call it 3 × 108.
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Hint 2 of 2
Turn 6.5 months into hours through friendly rounding: ≈ 200 days ≈ 5000 hours. Then speed ≈ distance ÷ time.
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Approach: round to easy numbers, divide
- First read the answer choices: they're spaced by powers of 10. That means precision is wasted — the game is to land in the right ballpark, so round everything to one digit.
- Distance ≈ 3 × 108 miles. Time: 6.5 months × 30 days ≈ 195 ≈ 200 days, and 200 × 24 ≈ 5000 hours.
- Speed ≈ (3 × 108) ÷ 5000 = 60,000 mph. Worth keeping: when choices differ by factors of 10, estimate aggressively and count zeros — chasing exact digits only costs time.
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