Problem 5 · 2001 AMC 8
Easy
Ratios, Rates & Proportions
distance-speed-timeestimate-and-pick
On a dark and stormy night Snoopy suddenly saw a flash of lightning. Ten seconds later he heard the sound of thunder. The speed of sound is 1088 feet per second and one mile is 5280 feet. Estimate, to the nearest half-mile, how far Snoopy was from the flash of lightning.
Show answer
Answer: C — 2 miles.
Show hints
Hint 1 of 2
The words "estimate" and "to the nearest half-mile" are permission to round — don't chase exact decimals.
Still stuck? Show hint 2 →
Hint 2 of 2
Find the distance the sound covered (speed × time) in feet, then ask which whole number of miles it's nearest.
Show solution
Approach: distance in feet, then convert to miles
- Sound travels distance = speed × time = 1088 × 10 = 10,880 feet during those 10 seconds.
- Now compare to miles: 2 miles = 2 × 5280 = 10,560 feet, which is the closest landmark — so the distance is about 2 miles.
- Worth keeping: sound covers roughly a mile every 5 seconds (≈5280 ÷ 1088). So "divide the delay by 5" gives miles — 10 seconds → ~2 miles, instantly.
Another way — the 5-seconds-per-mile rule:
- Each mile of sound takes about 5280 ÷ 1088 ≈ 5 seconds.
- A 10-second gap is two of those 5-second miles, so the lightning is about 2 miles away.
Mark:
· log in to save