How do you calculate combinations on the TI-84?

1 Answer
MeneerNask
Feb 9, 2015

I use a TI-83+ but the procedure will be the same.

The procedure is called nCr and it means:
From a group of n you select r while the order is not important.

Say you want to choose 3 students as class-representatives from a class of 25:

Recipe
Type in 25
Use the MATH-button and move to the PRB-menu (far right)
Choose nCr and enter
Type in 3 and enter
The answer (2300) will be the number of combinations.

BTW:
If the order is important (1st=president, 2nd=secretary, 3d=member), then you use nPr (=number of permutations) from the same menu (answer should be 13800)

The ratio between the two is the number of different orders that this selection can be in. (in this case 3! =6).
In other words: nPr= nCr *r!
Where n number to choose from, and r number to be chosen.

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