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Number System - Classification -2
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This video is second in the series of videos on number system. It contains classification on Natural number and an important concept based on that.

Vishal Sharma
I am an engineer by education and teacher by choice.I have been training students for CAT exams for 16 years.I have worked with top brands l

Unacademy user
im preparing for CSE 2018 anybody plz tell me. from which month i should start for studying current affair
Rohit Dadhich
a year ago
My opinion is you will start after reading my comment because current affairs are strengthen your basics and your views on topics which is beneficial for your mains preparation
Hungry Lion
a year ago
thnx
  1. Faculty : Vishal Sharma More than 16 years of experience in CAT training Trained 10000+ students till date


  2. Topic for Session NUMBER SYSTEM CONCEPT QUESTIONS BASED ON THEM


  3. Natural Number - Classificatiorn Prime Natural Number Co-Prime Composite Perfect


  4. Prime Numbers Numbers which are divisible by 1 and itself or Which has only two factors 1 is not a prime number 2 is the only even prime number 3,5,7 the only triplet All prime no are odd . All prime no greater than or equal to 5 are of the 6k+1 or 6k-1 Numbers from 1-50 15 From 51-100 10


  5. Let's look at some other types . Composite: Numbers which have more than 2 factors. Perfect Numbers whose sum of proper factors is equal to one. . Co-Prime : Factors which has only 1 as HCF Eg 5,6 8,11 1,30


  6. Let's take some more concept on Number:s How many total digits How many total digits do l use If I write from 1-1000 From 0-9,9*1-9 10 - 99,90* 2 180 100 999, 900*3 2700 1000- 4 digits do I use If I write from 1-100 From 0-9 9 single digit numbers From 10-99 90 two digit no 90*2 3 digits for 100 9*1 180 Total digits used 2893 Total digits used 192


  7. . How this concept can be Let's take up one more 1- 10000 No of digits used used in CAT? Suppose If I write digits sideways starting from 1234567891011. What is the unit digit of this 100 digit number? 1-999 = 2889 1000-9999 9000*4 = 36000 10000 5 digits Let's Look at the explanation Total 38894


  8. Explanation.... .Say from 1-9 9 *1-9 91 more digits.. From 10 to 54 there will be 45 numbers So 45*2 90 Next when we use 5 of next number 55 our 100 digit number is ready...So ans is '5


  9. Thank You