問PS gmat

夏雨荷 · 发表于 2022-3-28 14:46:50

1. Right triangle ABC is to be constructed in the xy-plane so that the right angle is at A and BC is parallel to the x-axis. The x and y coordinate of A, B, and C are to be integers that satisfy the inequalities -5<x<6 and 2<y<15. How many different triangles with these properties could be constructed? (求個詳解)
2. In an increasing sequence of 11 consecutive integers, the sum of the first 7 integers is 420. What is the sum of the last 7 integers in the sequence? (求個詳解)

18年杀G呗 · 发表于 2022-6-11 18:30:45

2、等差数列：设首项=a，前7个整数之和= 7(a+a+6)/2 = 7a+21=420，
后7个整数之和= 7(a+4+a+10)/2 = 7a+49 = 7a+21+28 = 420+28 = 448。

vegtam · 发表于 2022-6-12 16:34:46

第一题感觉没啥思路啊

問PS gmat

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