If the 5-digit number 535ab is divisible by 3, 7 and 11, then what is the value of (a2 - b2 + ab)?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 95
Concept
If a number is divisible by 3, 7 and 11, it must be divisible by 231.
Application
Let the highest number be 53599.
When divided by 231, it leaves a remainder as 7.
Thus, the number should be 53592 to be completely divisible by 231.
Thus, on comparing a and b with 53592, we get a = 9 and b = 2.
Putting the values of a and b in (a2 - b2 + ab)
( 81 - 4 + 18) = 95