Suppose you find seven equally useful articles related to the topic of your research paper. In how many ways can you choose five articles to read?

1st) You can read the 1st article in 7 ways

2d) You can read the 2nd article in 6 ways (because 1 is already chosen)

3rd) You can read the 3rd article in 5 ways (because 2 are already chosen)

4th) You can read the 4th article in 4ways (because 3 are already chosen)

5th) You can read the 5th article in 3 ways (because 4 are already chosen)

Total ways = 7x6x5x4x3 = 2520 ways

You can also find te solution in using the permutation formula

₇P₅ = (7!) / [ (7-5) !] = 2520 ways