4/14/10

Test 2 Section 5 - #16 (page 468)

For questions like this, it's best to just start listing the numbers that are "tri-factorable" (by listing numbers that are made by multiplying 3 consecutive positive integers, starting with the lowest positive integers we can). It won't take us long:

1 x 2 x 3 = 6
2 x 3 x 4 = 24
3 x 4 x 5 = 60
4 x 5 x 6 = 120
5 x 6 x 7 = 210
6 x 7 x 8 = 336
7 x 8 x 9 = 504
8 x 9 x 10 = 720
9 x 10 x 11 = 990
10x11x12 = 1320  (Oops, too high!)

So how many were under 1000?   9 of them.

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