AMC 8 2003 Problem 4
AMC8 2003 年第 4 题
方程与不等式★★☆☆☆
A group of children riding on bicycles and tricycles rode past Billy Bob's house. Billy Bob counted 7 children and 19 wheels. How many tricycles were there?
一群骑自行车和三轮车的孩子经过 Billy Bob 的家。Billy Bob 数了数，一共数到了 7 个孩子和 19 个轮子，那么有多少辆三轮车？
- A.2
- B.4
- C.5
- D.6
- E.7
正确答案 · Correct Answer
C
解析 · Solution
Solution 1
If all the children were riding bicycles, there would be 2×7=14 wheels. Each tricycle adds an extra wheel and 19-14=5 extra wheels are needed, so there are tricycles.
Setting up an equation, we have a+b=7 children and 3a+2b=19. Solving for the variables, we get, tricycles.
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