Question

Let abc be a three-digit number. Then abc – cba is not divisible by

• A. 9
• B. 11
• C. 18
• D. 33

Answer 1

The correct option is C 18

The general form of abc is 100a+10b+c.

The general form of cba is 100c+10b+a.

Now, (abc- cba) = (100a+10b+c) – (100c+10b+a) =99a-99c

= 99(a – c)

Now, abc – cba is divisible by 99, because 99 is the factor of abc – cba.

So, all the numbers which are the factors of 99 will also be divisible by abc-cba.

Here, 9, 11 and 33 are the factors of 99. But 18 is not a factor of 99. Hence abc- cba is not divisible by 18.