Permutations And Combinations Question 327

Question: Find the number of integral solution of the equation $ x+y+z=20 $ and $ x>-1,y>-2 $ and $ z>-3. $

Options:

A) $ ^{25}C _{23} $

B) $ ^{17}C_2 $

C) $ ^{23}C_2 $

D) None of these

Show Answer

Answer:

Correct Answer: A

Solution:

  • [a] Since as per the given condition $ x>-1, $ so x is non-negative integer, $ y>-2soy=-1+b $ and similarly $ z>3soz=-2+c $ or $ (x)+(-1+b)+(-2+c)=23 $ or $ x+b+c=23 $ And we need to find the number of non-negative integral solution of the equation $ x+b+c=23 $ which is, $ ^{23+3-1}{C _{3-1}}{{=}^{25}}C_2{{=}^{25}}C _{23} $