<p>Problem: <a href="http://i.imgur.com/8Fdek.jpg%5B/url%5D">http://i.imgur.com/8Fdek.jpg</a></p>
<p>I got this problem correct, but that was because I had about 6 whole minutes left at the end of the test after checking all of my work. I tried figuring out a strategy to tackle it, but ended up going the manual way (lol). </p>
<p>What's the ideal strategy for this problem?</p>
<p>Try reviewing Arithmatic Sequences . </p>
<p>I’ll try to come back and post a quick solution if no one answered you , but probablly tomorrow Cuz i need to log off now .</p>
<p>Use this formula-[n(n+1)]/2
So plug in 30(30+1)/2
it should give you 465.</p>
<p>To find t, you have to use the same formula but plug in this :
60(60+1)/2
=1830
1830-465=1365(value of t)
then just 1365-465=900.</p>
<p>I hope 900 is the right answer</p>
<p>t=31+32+…+60
s=1+2+…+30</p>
<p>Subtract term by term to get</p>
<p>t-s = 30+30+…+30 = 30*30=900</p>
<p>This is a standard SAT math strategy for subtracting large sums. Once you have a little practice you can do problems like this in 10 to 20 seconds.</p>
<p>Alright, thanks. And wow, I totally forgot to think of using the sum of arithmatic sequence formula.</p>
<p>@DrSteve: Wow, that’s pretty amazing! I’ll definitely keep that in mind if I ever see a problem like this.</p>
