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2003 AMC 10B Problem 4

Problem 4 of 25EasierAlgebraGeometryCounting & Probability

Rose fills each of the rectangular regions of her rectangular flower bed with a different type of flower. The lengths, in feet, of the rectangular regions in her flower bed are as shown in the figure. She plants one flower per square foot in each region. Asters cost $1\$1 each, begonias $1.50\$1.50 each, cannas $2\$2 each, dahlias $2.50\$2.50 each, and Easter lilies $3\$3 each. What is the least possible cost, in dollars, for her garden?

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Solution

The five regions have areas 4,4, 6,6, 15,15, 20,20, and 2121 square feet. Cost is minimized by placing the most expensive flower in the smallest region, so the total is (3)(4)+(2.5)(6)+(2)(15)+(1.5)(20)+(1)(21)=108. \begin{gathered} (3)(4)+(2.5)(6)+(2)(15) \\ {}+(1.5)(20)+(1)(21) \\ = 108. \end{gathered} Thus, the correct answer is A.

More practice

Concepts: area · optimization · pairing and grouping

Problem text and solution from the LIVE past-contest archive. See also the AoPS wiki page for community solutions.