Question 1210330
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The other tutors are using the combination formula.


I'll show an example calculation.
C(n,r) = (n!)/(r!(n-r)!)
C(7,3) = (7!)/(3!*(7-3)!)
C(7,3) = (7!)/(3!*4!)
C(7,3) = (7*6*5*4!)/(3!*4!)
C(7,3) = (7*6*5)/(3!)
C(7,3) = (7*6*5)/(3*2*1)
C(7,3) = 210/6
C(7,3) = 35
This indicates there are 35 ways to select 3 ripe tomatoes from a pool of 7 ripe tomatoes, where order doesn't matter. This assumes that we can distinguish the tomatoes apart.
C(7,3) = 35 is equivalent to saying 7C3 = 35.


Note that 35 is found in Pascal's Triangle. Locate the row that starts with "1,7,..."
In that row, move 3 spots to the right and you should land on 35. Specifically you should land on the first copy of 35. 
n = 7 tells us which row to look at, while r = 3 tells us how far to move to the right.


In GeoGebra, you would type <font color=blue>ncr(7,3)</font> to compute the combination value. 
Many other online calculators can be used as well. Or you can use a spreadsheet.
If you want to use Desmos, then you would input <font color=blue>nCr(7,3)</font> where the C <u>must</u> be uppercase and everything else lowercase.
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