My first ever game of bingo

 

I played bingo for the first time at the weekend. Once I got my head round it, I was fascinated by the numbers. I started to gather data far too late in the proceedings but found that on two rounds, it took 30 numbers out to get a line and 70 to get house. That from the maximum of 90. I was wondering whether it would be quicker to house with more people playing so I tried to calculate how many possible sets of 15 bingo numbers there are. The constraints were pointed out to me. There has to be something in each column which are set out units, tens, twenties etc. 6 columns have two numbers and 3 have only 1. I got 8.3 x 10^12. This wonderful website gives 24 x 10^15 - rather a lot more. I think they are asking a subtly different question because they factor in where the blanks go.