Shortcut Trick
Check Divisibility by 3 (sum of digits) and Divisibility by 11 (alternate digit difference).
For 10131: Sum = 1 + 0 + 1 + 3 + 1 = 6 (Divisible by 3).
Difference of alternate digits = (1 + 1 + 1) − (0 + 3) = 3 − 3 = 0 (Divisible by 11).
Since it satisfies both rules, the number is divisible by 33.
∴ The correct answer is 10131.
Alternate Method
Given: A number must be divisible by both 3 and 11.
Check each option systematically:
Option 1: 10010
⇒ Sum of digits = 1 + 0 + 0 + 1 + 0 = 2 (Not divisible by 3).
Option 2: 10131
⇒ Sum of digits = 1 + 0 + 1 + 3 + 1 = 6 (Divisible by 3 because 6 ÷ 3 = 2).
⇒ Sum of odd-position digits (1, 3, 5) = 1 + 1 + 1 = 3.
⇒ Sum of even-position digits (2, 4) = 0 + 3 = 3.
⇒ Difference = 3 − 3 = 0 (Divisible by 11).
⇒ 10131 is divisible by both 3 and 11.
Option 3: 10340
⇒ Sum of digits = 1 + 0 + 3 + 4 + 0 = 8 (Not divisible by 3).
Option 4: 10233
⇒ Sum of digits = 1 + 0 + 2 + 3 + 3 = 9 (Divisible by 3).
⇒ Sum of odd-position digits = 1 + 2 + 3 = 6.
⇒ Sum of even-position digits = 0 + 3 = 3.
⇒ Difference = 6 − 3 = 3 (Not divisible by 11).
∴ The correct answer is 10131.
Additional Information
Divisibility Rule of 3
A number is divisible by 3 if the sum of all its digits is divisible by 3.
Divisibility Rule of 11
A number is divisible by 11 if the difference between the sum of its digits at odd places and the sum of its digits at even places is either 0 or a multiple of 11.
Divisibility Rule of 33
Since 3 and 11 are co-prime, any number divisible by both 3 and 11 is also divisible by their product (3 × 11 = 33).