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2018 AMC 10A Problem 5

Problem 5 of 25EasierAlgebra

Alice, Bob, and Charlie were on a hike and were wondering how far away the nearest town was. When Alice said, “We are at least 66 miles away,” Bob replied, “We are at most 55 miles away.” Charlie then remarked, “Actually the nearest town is at most 44 miles away.” It turned out that none of the three statements was true. Let dd be the distance in miles to the nearest town. Which of the following intervals is the set of all possible values of d?d?

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Solution

Alice’s statement tells us that d<6.d \lt 6. Bob’s statement tells us that d>5.d \gt 5. Charlie’s statement tells us that d>4.d \gt 4. Combining all of these tells us that 5<d5 \lt d and d<6,d \lt 6, which means dd is in the interval (5,6).(5, 6). Thus, D is the correct answer.

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Concepts: logical deduction · inequality

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