Problem 1 · 1986 AJHSME
Easy
Ratios, Rates & Proportions
per-unit
In July 1861, 366 inches of rain fell in Cherrapunji, India. What was the average rainfall in inches per hour during that month?
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Answer: A — 366 ⁄ (31 × 24).
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Hint 1 of 2
You're asked for rain *per hour*, but the rain is given *per month*. What do you need to divide by to get from a month down to one hour?
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Hint 2 of 2
An average rate is always total amount ÷ total of the units you want — here, inches ÷ hours.
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Approach: average rate = total ÷ number of units
- "Per hour" is the giveaway: an average rate is the total spread evenly over every hour, so it's total inches ÷ total hours. No real arithmetic needed — just assemble the right division.
- How many hours in July? 31 days × 24 hours, so the answer is 366 ⁄ (31 × 24).
- Sanity check on the wrong options: anything that *multiplies* by 31 or 24 makes the rain bigger, but spreading it out over more time must make the per-hour figure *smaller* — only choice A divides.
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