【SAT官方每日一题】22/8/12 Mathematics > Standard Multiple Choice

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Mathematics > Standard Multiple Choice


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Read the following SAT test question and then click on a button to select your answer.
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+ e& A* |: N- pFor how many positive two-digit integers is the ones digit greater than twice the tens digit?


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B.
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D.
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+ X( m+ e* C/ {, h8 ~6 f# o4 Z正确答案:A

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The correct answer is (A). If the tens digit is 1, there are7  positive two-digit integers with the ones digit greater than twice the tens digit:
and 19. If the tens digit is 2 , there are 5  positive two-digit integers with the ones digit greater than twice the tens digit:  and 29. If the tens digit is 3 , there are 3 positive two-digit integers with the ones digit greater than twice the tens digit: and 39. If the tens digit is 4 , there is 4 positive two-digit integer with the ones digit greater than twice the tens digit:49 . If the tens digit is equal to or greater than 5, then the ones digits, which cannot be greater than  9 , is not greater than twice the tens digit. Therefore, there is a total of positive two-digit integers for which the ones digit is greater than twice the tens digit.




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