1) Regroup to subtract (29-Dec-06)
2) Regroup to subtract 1 (29-Dec-06)
3) Count up to subtract 2 (29-Dec-06)
4) Count up to subtract 1 (29-Dec-06)
5) Breaking minutes into hours and minutes (29-Dec-06)
6) Counting up time (29-Dec-06)
9) How many hours are there in a day? (29-Dec-06)