下面是是2011年2月18日的SAT官方每日一题的内容，是关于数学方面的，题型是选择。SAT官方每日一题是collegeboard每天都会发布的题目，关于SAT考试的三个部分的各个题型。下面我们就一起来看一下这个SAT官方每日一题吧。
SAT官方每日一题之数学---选择：
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Mathematics > Standard Multiple Choice
Read the following SAT test question and then click on a button to select your answer.
For how many positive two-digit integers is the ones digit greater than twice the tens digit?
A. 
B. 
C. 
D. 
E. 
The correct answer is A
Explanation
The correct answer is (A). If the tens digit is 
, there are 
positive two-digit integers with the ones digit greater than twice the tens digit: 
and 
. If the tens digit is 
, there are 
positive two-digit integers with the ones digit greater than twice the tens digit: 
and 
. If the tens digit is 
, there are 
positive two-digit integers with the ones digit greater than twice the tens digit: 
and 
. If the tens digit is 
, there is 
positive two-digit integer with the ones digit greater than twice the tens digit: 
. If the tens digit is equal to or greater than 
, then the ones digi
下面是一道和SAT官方每日一题相似的题目，供大家练习：
, 
, 
,
, ...
The first four terms of a sequence are shown above. Which of the following could be the formula that gives the 
th term of this sequence for all positive integers 
?
Answer Choices
(A) 
(B) 
(C) 
(D) 
(E) 
The correct answer is E
Explanation
If a formula gives the 
th term of the sequence for all positive integers 
, it must give the 
th term of the sequence for 
. If 
, then 
and 
, but the first term of the sequence is 
, so the general formula cannot be 
or 
. Also, if 
, then 
and 
, but the third term of the sequence is 
, so the general formula cannot be 
or 
. However, for 
, the values of 
are 
, 
, 
, 
, respectively. Therefore, the general formula for this sequence could be 
.
以上就是关于2011年2月18日SAT官方每日一题中数学选择的详细内容，包括了题目和选项以及答案，后面附有一道相关的练习题。大家可以在备考SAT的过程中关注SAT每日一题的内容，这样就可以更好有不间断的练习，也就能在日积月累的过程中得到提高。
更多SAT官方每日一题：
2011年2月20日SAT官方每日一题---改进句子
2011年2月21日SAT官方每日一题---数学选择
2011年2月22日SAT官方每日一题---完成句子
2011年2月23日SAT官方每日一题---句子改错
