That would be 6,740,000,000
We must find UNIQUE combinations because choosing a,b,c,d... is the same as d,c,b,a...etc. For this type of problem you use the "n choose k" formula...
n!/(k!(n-k)!), n=total number of choices available, k=number of choices made..
In this case:
20!/(10!(20-10)!)
20!/(10!*10!)
184756
B and a. it goes down about two lines and then has a very more steep incline
I think 50% or 1/2 ( it’s the same just one is in fraction and other in percentage)
