<p>This question is in the CB blue book on page 396, question #4. The question is as follows:</p>
<p>Bar graph that shows years and children each year: 1991 (0 children), 1992 (1), 1993 (1), 1994 (2), 1995 (3), 1996 (3), 1997 (5), and 1998 (5).</p>
<li>The graph (list really) shows how the Jackson family continued to grow between 1991 and 1998 by indicating the total number of children in the family at the end of each year. The Jacksons have one set of twins who were born to Mrs. Jackson one year in July. During what year were the twins born?
(A) 1993
(B) 1994
(C) 1996
(D) 1997
(E) 1998</li>
</ol>
<p>The answer is D. How can that be? It’s an easy question so I’m destined to fill stupid, but I don’t understand it. If it is 1997, then why couldn’t it be 1998 as well since they had five children both years?</p>
<p>Also, I don’t understand the next two either.</p>
<li>The average (arithmetic mean) of x and y is 5 and the average of x, y, and z is 8. What is the value of z?
(A) 19
(B) 14
(C) 13
(D) 11
(E) 3</li>
</ol>
<p>The answer is B, but I don’t know how. Perhaps I misunderstood the question.</p>
<li>If rstv = 1 and stuv = 0, which of the following must be true?
(A) r < 1
(B) s < 1
(C) t > 1/2
(D) u = 0
(E) v = 0</li>
</ol>
<p>The answer is D, but again… how can it be that? If it could be D, then why not E?</p>
<p>Looking at the diagram, you have a sudden increase from 3 to 5 from 1996 to 1997. In 1998, it’s still 5, which means that nothing changed. In 1996, they had three children; in 1997, they had 2 more(only point with an increase of +2). In 1998, they had no NEW children, it stayed the same. The twins were born in 1997, not 1998. </p>
<p>I think that for #5, you have to realize that x+y=10 because there are two terms and 2 multiplied by the average gives you the sum of the factors. For the next one, x+y+z=24 because 3* the average gives the sum. And I just told you that (x+y=10) so substitute that in to get 10+z=24 and z=14. For the next one, the letter V CAN’T be 0 because if it was, then RSTV would equal 0, but in this case, it’s equal to one. You can make up your own #s, though that is getting a little more complicated than you need to make it. R, S, T, and V=1, and that can be true. So then plug them all into the next one and you have 1<em>1</em>U*1=0. Divide by one and you get u=0.</p>
<p>Thanks Rahoul! I understand all three of the math questions now. I misinterpreted them. Like for #5, I randomly assumed that’s how many newborns they had each year. I should’ve thought realistically. Doh! Thanks again.</p>
<p>for the last one, just know that if 0 is anywhere in a multiplication problem, the answer is 0. V was in the problem before, and the answer was 1. If V had been 0, the answer couldn’t be 1.</p>