<p>I don't get the question nor the answer. Explaination please~!! This is from the Official Blue book, pg 842,Practice test 8, Section 2, Question 13</p>
<p>Q13. The first term of a sequence is 20 and the second term is 8. The third term and each term thereafter is the average (arithmetic mean) of the two terms immediately preceding it. What is the value of the first term in the sequence that is NOT an integer?</p>
<p>Correct ANSWER: 12.5, 25/2</p>
<p>????</p>
<p>Here's how I got it... you write out the sequence</p>
<p>20 8 (14) (11) (12.5)</p>
<p>You find 14 by adding 20 and 8, then dividing by two (28/2 = 14)</p>
<p>You find 11 by adding your new term 14 to 8, then dividing by two (22/2 = 11)</p>
<p>Then your next term, 12.5, you find by adding 11 and 14 and dividing by two (25/2 = 12.5)</p>
<p>Hope it helps :)</p>
<p>Okay. So the problem is giving you two numbers and telling you to take the average to get the third term. (20+8)/2 = 28/2 = 14. </p>
<p>Now you have the first three terms. The sequence is now 20, 8, 14. </p>
<p>Now, following the "take average of two preceding terms to get next term" rule, you take (8+14)/2 = 22/2 = 11. Okay, we still have integer answers, and the sequence is now 20, 8, 14, 11. </p>
<p>Next step is to continue the patten: (11+14)/2 = 25/2 = 12.5. Bingo! Our first non-integer answer. Just remember that an integer is a whole number, can be 0 or negative. </p>
<p>Make sense?</p>
<p>to find a number of a certain term, add the two numbers before it and divide by two (since your finding the average) ex. to find the 3rd term, add the first term (20) and the second term (8), then divide by 2.
first term - 20
2nd - 8
3rd - (20+8)/2 = 14
4th - (8+14)/2 = 11
5th - (14+11)/2 = 12.5</p>
<p>12.5 is not an integer since it is not a whole number.</p>
<p>Thanks alot guys. I got it.</p>