4 4 votes $N$ is the smallest number that has $5$ factors. How many factors does $N-1$ have? $4$ $6$ $5$ $3$ Quantitative Aptitude go-mockgate-1 factors quantitative-aptitude one-mark + – Ruturaj Mohanty 5.7k views answer comment Share Follow Print See 1 comment 1 1 comment reply Magma commented Dec 27, 2018 reply Follow flag A) 0 0 replyShare Please log in or register to add a comment.
Best answer 12 12 votes A number that has 5 factors has to be of the form x^4 where 'x' is a prime number. The smallest such number is 2^4 = 16 Therefore, N − 1 = 15. The factors of 15 are 1,3,5,15. So, N - 1 has 4 factors. So, Option (a) is correct.. ank73811 answered Dec 27, 2018 • selected Jan 17, 2019 by Shaik Masthan ank73811 comment Share Follow See all 3 Comments 3 3 Comments reply Doraemon246 commented Jan 5, 2019 i reshown by Doraemon246 Jan 5, 2019 reply Follow flag What if we choose a number by enumeration? The smallest natural number we obtain with 5 factors is $12$ $12$ has five factors - $1,2,3,6,12$ So $12-1 = 11$ has just 2 factors since it is prime i.e $1,11$ This does no seem to satisfy the property of the form $x^4$, yet it is the smallest number with 5 factors. Are we supposed to do anything different then? 1 1 replyShare Manoja Rajalakshmi A commented Jan 5, 2019 reply Follow flag @Doraemon246 4 is a factor of 12 4 4 replyShare Doraemon246 commented Jan 5, 2019 reply Follow flag My Apologies, Didn't consider that. 0 0 replyShare Please log in or register to add a comment.
