Last updated at Dec. 16, 2024 by Teachoo
Ex 7.1, 9 Write the natural numbers from 102 to 113. What fraction of them are prime numbers? Prime numbers Numbers which have only 2 factors – 1 & the number itself Eg: 2, 3, 5, 7……. Natural numbers from 102 to 113 = Finding prime numbers 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113 Divisible by 2 Number ending with 2, 4, 6, 8, 0 are divisible by 2 So, 102, 104, 106, 108, 110, 112 are not prime. Divisible by 3 If sum of digits is divisible by 3, It is divisible by 3 So, 105, 111 are not prime Rest all numbers are not divisible by 5, 7, 11 ∴ 103, 107, 109, 113 are prime Therefore, Total numbers = 12 Number of prime numbers = 4 ∴ Fraction = 𝟒/𝟏𝟐
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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo