The first one missed out on a number - It must be 0
4) http://web2.0calc.com/questions/how-to-calculate-compound-interest
5) http://web2.0calc.com/questions/evaluate30-mod-899
6) http://web2.0calc.com/questions/what-are-the-last-2-digits-of-7-2800
I think these one might be ok