※ 引述《a2515125 (Bobshih)》之銘言：
: How many hours did it take Helen to drive from her house to her parents' house?
: (1) Helen's average speed on this trip was 72 kilometers per hour.
: (2) If Helen's average speed on this trip had been 8 kilometers per hour greater, it would have taken her 1 hour less.
: 答案是C
: 請問如何列式？1+2
設總距離為X;需要的時間為Y
X/72=Y
X/80=Y-1
解聯立方程式求Y即可....
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