Question
CSATEasyPrelims 2018Reasoning

Consider the following sum: +1+2+3+1=21\bullet + 1 \bullet + 2 \bullet + \bullet 3 + \bullet 1 = 21 \bullet In the above sum, \bullet stands for

Explanation

Given the following sum: +1+2+3+1=21•+1•+2•+•3+•1=21• We need to determine what the symbol "•" represents.

Solution: Let "•" be denoted by nn. Rewriting the equation in terms of nn: n+1n+2n+n3+n1=21nn+1n+2n+n3+n1=21n Now, expand each term: n+10+n+20+n+10n+3+10n+1=210+nn+10+n+20+n+10n+3+10n+1=210+n Simplifying the equation: 23n+34=210+n23n+34=210+n Subtract nn from both sides: 22n+34=21022n+34=210 Now, subtract 34 from both sides:

22n=17622n=176 Solve for nn: n=8n=8.

Conclusion: The symbol "•" represents the digit 8.

Reasoning PYQs from 2018

Trusted by 2L aspirants

Practice UPSC Prelims PYQs Smarter

Practice Now
  • Track accuracy & weak areas
  • See past trends & repeated themes
Start Practicing Now

PYQs by Papers

Crack UPSC with your
Personal AI Mentor

An AI-powered ecosystem to learn, practice, and evaluate with discipline

SuperKalam
SuperKalam is your personal mentor for UPSC preparation, guiding you at every step of the exam journey.

Download the App

Get it on Google PlayDownload on the App Store
Follow us

ⓒ Snapstack Technologies Private Limited