<li> If the sume of the consecutive integers from -22 to x, inclusive is 72, what is the value of x?</li>
</ol>
<p>Anyone know how to do these type of questions?</p>
<p>ok, that's how I would try to solve it:</p>
<p>The sum is positive although we're starting with -22.
That means that x must be above 22 for SURE! (Because if x was 22 the sum would be 0.)</p>
<p>Now, just try:
If x was 23 the sum would be 23. Too low
...
If x was 25 the sum would be 23+24+25 = 72</p>
<p>Therefore the answer is 25 (I don't have the solution but I think I'm right :p)</p>
<p>well obviously from -22 to 22 is 0, so you just start adding from 23 until you get 72</p>
<p>I could not have said this better myself, chronic! ;)</p>
<p>ah, well that makes more sense than what I thought. Thanks guys.</p>
<p>I would do it this way..</p>
<p>the sum of numbers from 1 to n is equal to (n)(n+1) / 2
so from -22 to -1 = -253
therefore, to get back to zero you need to be at least +22, and then add 72, so:</p>
<p>(n)(n+1)/2 = 253+72 = 325
(n)(n+1)= 650</p>
<p>n = 25</p>