Problem 3 · 2023 AMC 8
Medium
Algebra & Patterns
evaluate-formula
Wind chill estimates how cold it feels in wind, using
(wind chill) = (air temperature) − 0.7 × (wind speed),
with temperature in °F and wind speed in mph. If the air temperature is 36°F and the wind speed is 18 mph, which is closest to the wind chill?
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Answer: B — About 23.
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Hint 1 of 2
‘Closest’ tells you not to sweat the decimals — estimate. Wind makes it feel colder, so your answer must come out below 36.
Still stuck? Show hint 2 →
Hint 2 of 2
Put the numbers into the formula: multiply 0.7 × (wind speed) first, then subtract that from the temperature.
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Approach: substitute into the formula, then pick the closest choice
- The word ‘closest’ is a hint that you can estimate. 0.7 × 18 is close to 0.7 × 18 = 12.6, and even rounding to ‘about 13 colder’ already points at choice (B).
- Exactly: 0.7 × 18 = 12.6.
- Subtract from the temperature: 36 − 12.6 = 23.4.
- Closest choice is 23. Sanity check: wind should make it feel colder, so the answer must be below 36 — it is.
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