Math question help, anyone?

Test Preparation SAT Preparation
1

<p>I honestly thought this was an easy question until I got to the answer choices:</p>

<p>For their graduation ceremony, the 100 students in Emily's senior class were each assigned a different positive integer from 10 to 100. Arlene and her classmates entered the auditorium in numerical order, and every 20 students filled a different row, maintaining that order. There were aisles on both ends of each row, and only one student sat between Emily and the aisle. Which of the following CANNOT be Emily's number?</p>

<p>A. 19
B. 42
C. 59
D. 69
E. 82</p>

<p>Answer was D. I honestly thought that it would be the answer choice not ending in either 9 or 2, a criterion all of these choices pass. Any idea why it's 69?</p>

2

<p>Yeah, you simply read the question too quickly :)</p>

<p>Although you are correct in your 9 or 2 assumption, it says that the rows fill up in groups of 20. Geddit now? The answer cannot be within two of a multiple of 20 (which 70 is not).</p>

3

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<p>Oh, wow. Better this mistake on practice tests than the real thing!</p>

4

<p>Whoops, I meant to say “has to be within a multiple of 20” instead of “cannot be”… haha.</p>