CAT Quantitative Aptitude Questions | CAT Number Theory - Sum of first N natural numbers

CAT Questions | Number Theory | Sum of first N numbers
CAT Questions

The question is about Sum of first N natural numbers. Application of sum of first N numbers. We need to do trial and error to arrive at the answer. Dealing with digits and base system of a number is a vital component in CAT Number Theory. A range of CAT questions can be asked based on this simple concept in the CAT Exam.

Question 2: A page is torn from a novel. The sum of the remaining page numbers is 10000. What are the two page-numbers on the torn page of this novel?

1. 77 and 78
2. 33 and 34
3. 8 and 9
4. None of these

Best CAT Coaching in Chennai

CAT Coaching in Chennai - CAT 2020Online Batches Available Now!

Method of solving this CAT Question from Number Theory - Digits: Number Theory questions make us go from rigour to trial-and-error alternately. This is one such question.

$$frac{n$n+1$}{2}$ should be nearby 10,000, so n$n + 1) is somewhere near 20,000.
So n should be around √(20000) about 141.
Try 142
142 * 143 = 10153
141 * 142 = 10011
So, the missing pages are either 76 and 77 or 5 and 6.

The question is "What are the two page-numbers on the torn page of this novel?"

Hence the answer is "None of these"

Choice D is the correct answer.

CAT Coaching in ChennaiCAT 2020Enroll at 35,000/-

Online Classroom Batches Starting Now!

Best CAT Coaching in ChennaiRegister Online, get Rs 7000/- off

Attend a Demo Class

CAT Online Coaching | CAT Number Systems questions Videos On YouTube

Other useful sources for Number System Questions | Number Theory HCF and LCM Sample Questions

Where is 2IIM located?

2IIM Online CAT Coaching
A Fermat Education Initiative,
58/16, Indira Gandhi Street,
Kaveri Rangan Nagar, Saligramam, Chennai 600 093

How to reach 2IIM?

Phone: (91) 44 4505 8484
Mobile: (91) 99626 48484
WhatsApp: WhatsApp Now
Email: prep@2iim.com