Question 864622
Order is important, so we use a permutation. 



P(n,r) = (n!)/((n-r)!)


P(25,12) = (25!)/((25-12)!)


P(25,12) = (25!)/(13!)


P(25,12) = (25*24*23*22*21*20*19*18*17*16*15*14*13!)/(13!)


P(25,12) = 25*24*23*22*21*20*19*18*17*16*15*14


P(25,12) = 2,490,952,020,480,000



The answer is 2,490,952,020,480,000 which is the number 2 quadrillion 490 trillion 952 billion 20 million 480 thousand (definitely a big number). A shorter way to say it is to round to the nearest trillion to get 2.491 quadrillion.



The answer in scientific notation is 2.49095202048 * 10^15 and that can be shortened to 2.491 * 10^15