Problem 9 · 2002 AMC 8
Medium
Arithmetic & Operations
read-tablecareful-counting
Juan organizes the stamps in his collection by country and by the decade in which they were issued. He paid these prices at the stamp shop: Brazil and France, 6¢ each; Peru, 4¢ each; and Spain, 5¢ each. (Brazil and Peru are South American countries; France and Spain are European.) The table shows how many stamps he has from each country and decade.
His South American stamps issued before the 1970s cost him how much?
| Country | '50s | '60s | '70s | '80s |
|---|---|---|---|---|
| Brazil | 4 | 7 | 12 | 8 |
| France | 8 | 4 | 12 | 15 |
| Peru | 6 | 4 | 6 | 10 |
| Spain | 3 | 9 | 13 | 9 |
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Answer: B — $1.06.
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Hint 1 of 2
Turn each phrase into a filter before touching numbers: "South American" = Brazil & Peru rows; "before the 1970s" = the '50s and '60s columns (the '70s is *not* before itself).
Still stuck? Show hint 2 →
Hint 2 of 2
Brazil and Peru cost *different* amounts, so keep them separate: count each country's stamps, multiply by *its own* price, then add the two costs.
Show solution
Approach: count the right cells, then multiply by price
- Filter first: rows Brazil & Peru, columns '50s & '60s. That's a 2-by-2 block of four cells.
- Cost stays per-country because the prices differ. Brazil: 4 + 7 = 11 stamps × 6¢ = 66¢. Peru: 6 + 4 = 10 stamps × 4¢ = 40¢.
- Total: 66¢ + 40¢ = 106¢ = $1.06.
- *Watch-out worth keeping:* don't add stamp counts across rows that have *different* unit prices — total each price group on its own, then combine. Mixing them is the classic table-problem slip.
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