<p>Kevin is 3 years younger than nora. If n represents noras age now, what was kevins age 4 years ago in terms of n?
a. n+7
b. n+1
c. n-1
d. n-4
e. n-7</p>
<p>The answers E but i chose D by setting up this eqn. K+3=n , so K-1 = n-4 , so n-4 must be kevins age 4 years ago. K+3=n correctly defines kevin being 3 years younger than nora, but why is this answer incorrect? why does it have to be n-3=k? Can somebody please explain</p>
<p>It's asking for 4 years ago, not one year ago. K-1 is kevin's age one year ago.</p>
<p>Yes, K is Kevin's age now, so K-1 = n-4, so Kevin's age one year ago is Nora's age 4 years ago. And Kevin's age 4 years ago is K-4 = n-7.</p>
<p>K + 3 = N that's good
K = N - 3 makes sense
K - 4 = N - 7 taking away four years.</p>
<p>Here, K represents Kevin's age now. So you need K - 4 for Kevin's age four years ago.</p>
<p>Thanks but what exactly does K+3=n represent then?</p>
<p>K+3 = n represents the relationship between Kevin's and Nora's age now.</p>
<p>I usually do these questions with a 2 by 2 chart for "now" and "then"</p>
<p>..........NOW ............ THEN
Kevin.....k..................k-4
Nora......n..................n-4</p>
<p>But, since you know K+3 = n, or in other words, K=n - 3, you can substitute that fact in as needed.</p>
<p>Kevin's age "then" is k - 4
But, you want Kevin's age in terms of n, so sub in k = n-3 to get
Keven's age "then" is (n - 3) - 4, or n - 7</p>
<p>The easiest way to do these is to just pick values... </p>
<p>For example, lets just say that Kevin is 15. Therefore, Nora must be 18, becuase she is three years older than Kevin. So, k = 15 - 4, which is 11. Eleven is equal to Nora's age minus seven years. Problem solved.</p>
<p>^ agreed. plug in values whenever you can. Especially on those number 16-17 relation problems with no numbers at all.</p>
<p>Why don't you just think: Kevin is 3 years younger than Nora now. 4 years ago Kevin would be 7 years younger than Nora is now. Nora's age now is n and Kevin would be 7 years younger 4 years ago so n-7 makes sense. Takes 10 seconds. </p>
<p>Formulas aren't necessary. I guess that's not entirely true... For the vast majority of word problems if you translate the English into an equation it helps. Just make sure you understand what the equation represents and what's going on.</p>
<p>^ I agree, but usually I find it easier to think of variables. Doing that takes 10 seconds too.</p>
<p>K + 3 = N
K - 4 = N-7 and that's it.</p>
<p>Thanks everyone, i got it.</p>
<p>actually liebenasuka, one year ago would be k-4........
N-3=K
Nora's age - 4= K's age 4 years ago</p>
<p>N-3-4=K
N-7=K
E</p>
<p>
[quote]
one year ago would be k-4........
[/quote]
you mean n-4?</p>
<p>gatorfan, you contradicted yourself. You put N-3 = K and then N-3-4 = K.</p>