Question

how many 3 digit numbers can be formed with 2 consecutive same numbers .
a>160 b> 171 c> 180 D> 256

Answer 1

because

if you fix the 2nd and 3rd position which can be done in 10 ways and 1st position can take value from 1-9 therefore total ways comes out to b 9*10=90

plus

if you fix the 1st nd 2 position which can be done in 9 ways and 3rd position can take 10 values i.e from 0-9, that makes it 9*10=90

total=90+90=180

now minus the common part like 111,222 to 999

that is total of 9 numbers..

therefore finally 180-9=171

Ans---> 162