Q. How many 10 digit numbers can be written by using the digits 1 and 2?
A) $\ ^{10}C_{1} + \ ^{9}C_{2}$
B) $2^{10}$
C) $\ ^{10}C_{2}$
D) $10!$
Explanation
(b)
Each digit can be placed in 2 ways.
$\therefore$ Required number of ways $= 2^{10}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.