<p>1- a= 1 x 2 x 3 x .... n
b= 3 x 4 x 5 x ....n-1, then a/b=
A) 2n-2
B) 2n-1
C) n-2
D) n
E) 2n</p>
<p>Kindly, include your answer explanation.</p>
<p>2n.</p>
<p>I find it easiest to quickly plug in numbers to see what you get.</p>
<p>For example, look at the case where n=7:</p>
<p>(1<em>2</em>3<em>4</em>5<em>6</em>7) / (3<em>4</em>5<em>6) = 2</em>7 (everything else cancels out), which means 2n in general terms.</p>
<p>Does that make sense to you?</p>
<p>yes, Thanks alot !</p>
<p>Quickest solution:</p>
<p>When you divide a by b you can cancel any factors that are the same. </p>
<p>3, 4, …, n-1 are factors of both a and b. So</p>
<p>a/b = 1<em>2</em>n = 2n.</p>