<p>There's a sample math question on page 24, number 6. Permutation type thing, I think?</p>
<p>How many different three-digit numbers greater than 240 can be formed by using three different digits from the set {1, 2, 3, 4}></p>
<p>How would you do this problem the fast way?</p>
<p>241
312
321
341
314
412
413
421
423
431
432
11</p>
<p>Still, it would be better to have a fast way. I’m confused too…</p>
<p>The actual answer is twelve… You missed 243. There’s probably something to the fact that there are four numbers… 4 times 4 is 16. Any number starting with 1 can’t work. So minus four. Not sure… But the way that I know is right is to just list all the numbers…</p>
<p>Just kidding… answer is 14… I actually checked this time by listing them out…
241 243 312 314 321 324 341 342 432 431 423 421 412 413</p>