Question

How many no can be formed using digits (1,2,3,4,5,6,7,8,9) such that they are in increasing order (eg:0 12345, 345, 6789,
123456789)?
O A. 32
B. 36
O C.' 25
OD. 30​

Answer 1

Answer:

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:

29−1=511