PP1 (Shorter) Quant Section 2 (Medium) Q15

<p><span style="color:#27ae60;"><span style="font-size:20px;">Solving The Problem</span></span></p> <p>Let&#39;s go <span style="color:#8e44ad;"><strong>Piece by Piece</strong></span>, reading slowly and making deductions:</p> <blockquote> <p>The average (arithmetic mean) of the II numbers in a list is 14.</p> </blockquote> <p>We know about the following relationship between mean and sum: $sum = mean * \#\,values$</p> <p>Since we know the mean and the number of values, let&#39;s work out the sum of this list:</p> <ul> <li>$sum = 14 * 11$</li> <li>$sum = 154$</li> </ul> <blockquote> <p>If the average of 9 of the numbers in the list is 9,</p> </blockquote> <p>We can do the same process and work out the sum of these $9$ numbers:</p> <ul> <li>$sum\,of\,9\,numbers= 9 * 9$</li> <li>$sum\,of\,9\,numbers = 81$</li> </ul> <p>We can also deduce the following:</p> <ul> <li>$sum\,of\,11\,numbers = sum\,of\,9\,numbers + sum\,of\,remaining\,two\,numbers$</li> <li>$154 = 81 + sum\,of\,remaining\,two\,numbers$</li> <li>$73 = sum\,of\,remaining\,two\,numbers$</li> </ul> <blockquote> <p>what is the average of the other 2 numbers?</p> </blockquote> <p>Now, we can use the relationship between sum and mean one last time to figure out the average of these two numbers:</p> <ul> <li>$mean\,of\,remaing\,two\,numbers = \frac{sum\,of\,remaing\,two\,numbers}{\#\,values}$</li> <li>$mean\,of\,remaing\,two\,numbers = \frac{73}{2}$</li> <li>$mean\,of\,remaing\,two\,numbers = 36.5$</li> </ul> <p>So, the answer is <span style="color:#27ae60;">36.5</span>.</p>