The Number Of Natural Numbers Which Are Smaller Than 2 × 108 and Which Can Be Written By Means Of The Digits And 2 Is ………..

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The number of natural numbers which are smaller than 2 × 108 and which can be written by means of the digits and 2 is ………..


Correct option is


The required number are 1, 2, 11, 12, 21, 22, …, 122222222. 

Let us calculate how many numbers are these.

There are 2 one digit such numbers. There are 22 two digit such numbers. And so on. 

There are 28 eight digit such numbers. All the nine digit numbers beginning with 1 and written by means of 1 and 2 are smaller than 2.108. Thus, there are 28 such nine digit numbers. 

Hence, the required number of numbers is  





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