99 Percentile Qs Bank for JEE MainMathematicsPermutation and Combination
There are 10 red and 5 yellow roses of different sizes. If x is the number of garlands that can be formed with all these flowers so that no two yellow roses come together and y is the number of garlands formed with all these flowers so that all the red roses coming together, then 2 x - y 10 ! =
Options
- A9 ! 5 ! - 5 !
- B11 2 · 4 !
- C10 ! - 6 !
- D6 ! × 5 ! - 2
Correct answer
A. 9 ! 5 ! - 5 !
Step-by-step solution
Given that 10 Red roses & 5 Yellow roses. x is number of garlands that can be formed with all these flowers so that no two yellow roses come together. i.e., first arranging 10 Red roses in 9 ! 2 then in that 10 gaps we can arrange these 5 yellow roses in 10 ! 5 ! = 10 × 9 × 8 × 7 × 6 . So x = 9 ! 2 × 10 P 5 y is number of garlands with all these flowers so that all the red roses coming together. i.e., taking all red roses as one unit and arranging red and yellow roses is y = 5 ! 2 × 10