Subject: General Aptitude · Chapter: Number System
The number 311311311311311311311 is
(a)neither divisible by 3 nor by 11
(b)divisible by 11 but not by 3
(c)divisible by 3 but not by 11
(d)divisible by both 3 and 11
Answer
Answer (as printed): A
Explanation
Sum of the digits of the given number = (7 × 3) + (14 × 1) = (21 + 14) = 35, which is not divisible by 3. So the given number is not divisible by 3. 41 Also, (1 + 3 + 1 + 1 + 3 + 1 + 1 + 3 + 1 + 1 + 3) – (1 + 1 + 3 + 1 + 1 + 3 + 1 + 1 + 3 + 1) = (19 – 16) = 3, which is neither 0 nor divisible by 11. So, the given number is not divisible by 11 also. Hence, it is divisible by neither 3 nor 11.
Explanation as extracted from the printed page; notation may be imperfect.