0 votes 0 votes Set A is formed by selecting some of the numbers from the first 100 natural numbers such that the HCF of any two numbers in the set is 5. What is the maximum number of elements that A can have? a)7 b)8 c)9 d)10 Sambhrant Maurya asked Jul 28, 2018 Sambhrant Maurya 1.1k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes A={5,10,15,25,35,55,65,85,95} consider product of a prime number and 5 which will give you the set and since range is 1 to 100 we will have 9 elements. (including 5 also) so answer is C. arvin answered Jul 28, 2018 arvin comment Share Follow See all 2 Comments See all 2 2 Comments reply Sambhrant Maurya commented Jul 28, 2018 reply Follow Share Why 5 X prime numbers? Why not 5 X natural numbers? 0 votes 0 votes arvin commented Jul 28, 2018 reply Follow Share because it will violate the hcf being only 5.. for eg. if you take 15 and 45... hcf will be 15 not 5.. take some example and go through definition of hcf... it will help :p 0 votes 0 votes Please log in or register to add a comment.