2013年12月06 SAT官方每日一题-川外培训官方网站

2013年12月06 SAT官方每日一题

2013-12-08 16:29 | 编辑：川外教育　　来自：未知　

导读：考试类型: Mathematics Standard Multiple Choice Read the following SAT test question and then click on a button to select your answer. The sum of the positive odd integers less than is subtracted from the sum of the positive even integers l

考试类型: Mathematics > Standard Multiple Choice

Read the following SAT test question and then click on a button to select your answer.

The sum of the positive odd integers less than is subtracted from the sum of the positive even integers less than or equal to . What is the resulting difference?

D. 100

E. 200

正确答案:B

解析:

The sum of the positive odd integers less than is 1 + 3 + 5 + ... + 45 + 47 + 49 , and the sum of the positive even integers less than or equal to is 2 + 4 + 6 + ... + 46 + 48 + 50 . When the first sum is subtracted from the second, the terms can be regrouped to form (2 minus 1) plus (4 minus 3) + ... + (48 minus 47) + (50 minus 49) , which is just 1 + 1 + 1 + ... + 1 , where there are ones. Therefore, the correct answer is .