Question

How many four digits numbers are there which contains not more than two different digits?

• A. $444$
• B. $144$
• C. $576$
• D. $289$

Answer 1

Answer: (C)

$576$

Consider hundred's, ten's and units digits in the case that there are two distinguished in the number

with exactly two different places $(2^3-1)=7$ways

$9\times 9$ways of choosing the pair of digits

Total possibilities

$=9\times 9\times 7+9=576$