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30 Choose 5 = 30C5 = 142506
Start with 30, then multiply by 1 less, then by 1 more less, etc.
until you have 5 factors on top,
Then have a hay-day of canceling
Cancel the 5 into the 30, get 6.
Cancel the 4 into the 28, getting 7.
Cancel the 3 into the 29, getting 9.
Cancel the 2 into the 26, getting 13.
6 7 9 13
1 1 1 1
So it's 6×29×7×9×13 = 142506
If you have a TI graphing calculator, you can do this
type 30
press MATH
Press the left arrow key <-
Press
3 (Should see 30 nCr
type 5 (Should see 30 nCr 5
press ENTER
See 142506
Edwin