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The number of n digit numbers which consists of the digit 1 & 2 only if each is to be used at least once, is equal to 510 then n is equal to_____ (A) 7 (B) 8 (C) 9 (D) 10 Please explain step by step.

```
8 years ago

Arun Kumar
IIT Delhi
256 Points
```							Hi$no. with atleast once occurrence  \\=>total -no occurrence of 1 -no occurrence of 2 \\=>2^n-2=510 \\=>2^n=512 \\=>n=9$Thanks & Regards, Arun Kumar, Btech,IIT Delhi, Askiitians Faculty
```
6 years ago
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### Course Features

• 101 Video Lectures
• Revision Notes
• Test paper with Video Solution
• Mind Map
• Study Planner
• NCERT Solutions
• Discussion Forum
• Previous Year Exam Questions