How many no can be formed using digits (1,2,3,4,5,6,7,8,9)..such that they are in increasing order?

• Consider the string 123456789. Observe that each of the 9 digits in the string can safely be either included or not included, since failing to include a digit will not violate the increasing order of the digits. Hence, there are 29 possible strings that contain (0 or 1 or 2 or ... or 9) digits. However, we likely want to omit the case where there are 0 digits, which leaves us with a final answer of:
  
  2^9 -1 = 511
  
  
• 9 years agoHelpfull: Yes(5) No(0)
• if we include all no at a time then only one no is possible 1 2 3 4 5 6 7 8 9
• 9 years agoHelpfull: Yes(3) No(2)
• i think 502 is the answer as in the last sol i have only consider case for 3 digit no bt there can be any no which includes 2,3,4...9 digit no
• 9 years agoHelpfull: Yes(2) No(0)
• i think 9c3=84 is the answer as there is only one way to arrange the order.
• 9 years agoHelpfull: Yes(0) No(3)