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05 Feb 2021, 03:00
Kudos
Bookmarks
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
75%
(hard)
Question Stats:
51% (01:55) correct
49%
(02:16)
wrong
based on 184
sessions
History
Date
Time
Result
Not Attempted Yet
In how many ways can 4 identical red balls and 5 different green balls be arranged in a line such that no two red balls are together?
A. 5*5!
B. 6*5!
C. 15*5!
D. 5*4!*5!
E. 6*4!*5!
A. 5*5!
B. 6*5!
C. 15*5!
D. 5*4!*5!
E. 6*4!*5!
05 Feb 2021, 06:35
Kudos
Bookmarks
Bunuel
Let's imagine a situation where there is one emply space between every two green balls
_ G _ G _ G _ G _ G _
Now, we have total 6 empty spaces out of which any 4 can be taken by red balls so that no two. of them are ever together
But we need only 4 spaces as we have only 4 red balls so total ways of choosing 4 spaces out of 6 \(= 6C4 = 15\)
Now, ways of arranging red balls at chosen spaces = 1 (all red balls are identical)
Now, ways of arranging Green balls at their places = 5! (all Green balls are different)
Total Outcomes \(= 6C4*1*5! = 15*5!\)
Answer: Option C
General Discussion
