Question

Katy is making 2-layer dip for a party and has 10 ingredients from which to choose. In how many ways can she pick out and layer 2 ingredients?

Answer 1

45

Explanation:

10!/(10-2)!*2!

10!=1*2*3*4*5*6*7*8*9*10=3628800

8!=1*2*3*4*5*6*7*8=40320

2!=1*2=2

3628800/40320*2

3628800/80640=45