新人求助problem solving

vincent815 · 发表于 2010-4-4 18:32:00

A travel agent offers a vacation plan which costs z dollars for the first day, and z/6 dollars for each additional day. How much does a vacation of y days cost, in dollars, where y > 1 ?

vincent815 · 发表于 2010-4-4 18:33:28

答案是（y2 + 5yz + z2）/3

vincent815 · 发表于 2010-4-4 18:37:41

A riverboat leaves Mildura and travels upstream to Renmark at an average speed of 6 miles per hour. It returns by the same route at an average speed of 9 miles per hour. What is its average speed for the round-trip, in miles per hour?
答案是7.2

vincent815 · 发表于 2010-4-4 18:38:58

第一题看错答案了，不好意思，上面一题怎么做的麻烦教下

freedombringer · 发表于 2010-4-4 19:06:09

第二题
假设2点路程是S，那么来回就是2S
逆流而上的时间是S/6，顺流回来的时间是S/9,那么平均速度是2S/(S/6+S/9)

新人求助problem solving

所属分类: GMAT考试

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