Q. If $\ ^{189}C_{35} + {\ ^{189}C}_{x} = \ ^{190}C_{x}$, then $x$ is equal to
A) 34
B) 35
C) 36
D) 37
Explanation
(c)
$\because\ \ \ \ ^{n}C_{r} + \ ^{n}C_{r - 1} = \ ^{n + 1}C_{r}$
$\therefore\ \ \ \ ^{189}C_{36} + \ ^{189}C_{35} = \ ^{190}C_{36}$
But $\ ^{189}C_{35} + \ ^{189}C_{x} = \ ^{190}C_{x}$
Hence, value of $x$ is 36
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.