SOLUTION: 20C3 combination equation. without using a calculator professor said this tactic gives right answer but there is a shorter way 20*19*18*17*16*15*14*13*12*11*10*9*8*7*6*5*4*3*2*1/

Algebra ->  Exponents -> SOLUTION: 20C3 combination equation. without using a calculator professor said this tactic gives right answer but there is a shorter way 20*19*18*17*16*15*14*13*12*11*10*9*8*7*6*5*4*3*2*1/      Log On


   

Question 377920: 20C3 combination equation. without using a calculator
professor said this tactic gives right answer but there is a shorter way
20*19*18*17*16*15*14*13*12*11*10*9*8*7*6*5*4*3*2*1/(20-3)!*3!
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
Since 20C3+=+20%21%2F%2817%21%213%21%29 we can write 20! as 20*19*18*17! Cancel the 17! from both sides to get
20C3+=+%2820%2A19%2A18%29%2F3%21+=+20%2A19%2A6+=+2280