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

1.	Let abc be a three-digit number. Then abc – cba is not divisible by(a) 9 (b) 11 (c) 18 (d) 33
Answer» The correct answer is option (c) 18 Explanation: The general form of abc is 100a+10b+c The genera form of cba is 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.

Let abc be a three-digit number. Then abc – cba is not divisible by(a) 9 (b) 11 (c) 18 (d) 33

Answer»

The correct answer is option (c) 18

Explanation:

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

The genera form of cba is

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.