<p>If a, b, and a c are numbers such that a/b=3 and b/c=7, then (a+b)/(B+C) is equal to which of the following?
The answer is 7/2 but I didn't get the explanation. Help?</p>
<p>Just pick numbers and plug them in -</p>
<p>a/b = 3, so make a=3 and b=1</p>
<p>b/c = 7, so make b=1 and c=1/7</p>
<p>now just plug them in to their terms –> (3+1)/(1+1/7) –> (4)/(1.143) —> 7/2 or 3.5</p>
<p>ahhh. I see. Thanks</p>
<p>If a, b, and a c are numbers such that a/b=3 and b/c=7, then (a+b)/(B+C) is equal to which of the following?
The answer is 7/2.</p>
<p>If a/b=3, you can just use cross-multiplying. a/b=3/1, so a=3b.</p>
<p>If b/c=7, convert it to make it easy: b/c=7/1, which means b=7c.</p>
<p>Then, plug this new info into the first equation. a=3b=3(7c)=21c.</p>
<p>Now, substitute the (a+b)/(b+c) to make every variable in terms of c.</p>
<p>(21c+7c)/(7c+c)=28c/8c=28/8=7/2. :)</p>
<p>I don’t know if this will work. You can put everything in terms of B and then continue solving for all the variables and then plug them into the final equation. There should be a better way though.</p>