How many ways can 12 people out of 300 be selected for a jury?
This is the combinations of 300 things taken 12 at a time.
This is sometimes written C(300,12) and sometimes 300C12
Checkley's answer is wrong as he thought it was permutations,
but because the order of the members of a jury is not important,
we must use combinations, not permutations, which means we
must divide his answer by 12! or 12·11·10·9·8·7·6·5·4·3·2·1 =
479001600.
So Checkley should have had
300*299*298*297*296*295*294*293*292*291*290*289 4.252707522E29
------------------------------------------------- = ----------------- =
12*11*10*9*8*7*6*5*4*3*2*1 479001600
4.252707522 × 1029
--------------------- = 8.878274148 × 1020
479001600
Here is how to do it on a TI-83 or TI-84 calculator:
Type in 300
Press MATH
Press |
Press 3 (You should see this on the main screen: 300 nCr
Type in 12 (You should see this on the main screen: 300 nCr 12
Press ENTER
Read this: 8.878274148E20
This means 8.878274148 × 1020
or about
887,827,414,800,000,000,000
887 quintillion, 827 quadrillion, 414 trillion, 800 billion
Edwin
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