A owes B Rs.50. He agrees to pay B over a number of consecutive days on a Monday, paying single note or Rs.10 or Rs.20 on each day. In how many different ways can A repay B.\nOptions:\n(A) 2\n(B) 8\n(C) 9\n(D) 6\n(E) 5 OK. Let's think. Some random thoughts first:
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He can pay by all 10 rupee notes = 1 way\n3 Ten rupee + 1 twenty rupee = 4!3!×1!4!3!×1! = 4 ways\n1 Ten rupee + 2 twenty rupee notes = 3!2!×1!3!2!×1! = 3 ways\nTotal ways = 1 + 4 + 3 = 8 The answer: (B).
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