Question

the sum of all digits of 100n- n is 512.If n is a 2 digit number then what is the value of n?​

Answer 1

Step-by-step explanation:

Answer

Correct option is

C

9

Basically we have n blank spaces in which we have to put 1 and 2

∴ Total such occurance =2

n

But we have to subtract the cases where there is no occurance of 1 and no occurance of 2

Hence, Number with atleast one occurance

=2

n

−1−1=2

n

−2

2

n

−2=510 ⇒n=9