A puzzle…

Does any subset of these numbers add to 50? {27, 25, 3, 12, 6, 15, 9, 30, 19, 21} Generalize the problem: S  I N = {n 1, n 2,…n k }, n i  I M  N   n i = S M

Another puzzle… M&F, p. 113

Crossing the ravine 4 men, A, B, C, D need to cross a dangerous bridge over a ravine at night. They have one light which must be used for crossing. The bridge can only take the weight of two men at once. How quickly can all four cross the bridge? A can cross in 1 min, B 2, C 5, D 10. A B C D