Question

All the numbers from 1 to 99 are multiplied together. Use a pattern to determine the last digit of the product. Justify your answer.

Answer 1

I do not know how to figure out the pattern, but when you do you can justify your answer by saying multiplying all the numbers together is exactly the problem "99!" which you can punch in to a calculator. I hope this is right and makes sense :/

Answer 2

1 + 99
2 + 98
3 + 97
...............
...............
49 51
+ 50

49(100) + 50