https://web2.0calc.com/questions/cphill-help-the-multiplication-principle-in-counting
My classroom has 11 rows of chairs, with 11 chairs in each row. The chairs in each row are numbered from 1 to 11. How many chairs have odd numbers?
We have 11 * 11 = 121 chairs
So....the number of "odd" ones = 120/2 + 1 = 60 + 1 = 61
+-276 
