1. (a) 56 (b) 61 (c) 400
2. (a) 48, 48 (b) 0.81 (c) (0.1)^20, 2
3. (a) 0.02; (b) 0.21; (c) 2/21
4. (a) (20*19*18)/(40*39*38) (b) (20*19*18)/(40*39*38)  (c) 3/2
5. (a) 2/3 (b) 1/3