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Which of the following numbers is completely divisible by 11?
1331
1441
1211
1342
1331
Calculate the difference between the sum of digits at odd places and even places. If the result is 0 or divisible by 11, the number is divisible by 11.
Four numbers are provided: 1331, 1441, 1211, and 1342.
Sum┬аof┬аodd┬аpositionsтИТSum┬аof┬аeven┬аpositions=0┬аor┬аmultiple┬аof┬а11
Calculate the difference between the sum of digits at odd places and even places. If the result is 0 or divisible by 11, the number is divisible by 11.
Students often confuse odd/even positions by counting from left to right; the rule works from either direction as long as the alternating sign pattern is consistent.
Analyze Option A (1331)
Identify digits at odd positions (1, 3) and even positions (3, 1). Calculate sum of odd positions = 1+3=4 and sum of even positions = 3+1=4.
тИг4тИТ4тИг=0
Analyze Option B (1441)
Digits at odd positions (1, 4) sum to 5. Digits at even positions (4, 1) sum to 5. Wait, let's recheck: 1тИТ4+4тИТ1=0. Actually, 1441 is also divisible by 11 (11├Ч131=1441).
1тИТ4+4тИТ1=0
Analyze Option D (1342)
Digits at odd positions (1, 4) sum to 5. Digits at even positions (3, 2) sum to 5. Actually, 1342/11=122, so 1342 is also divisible by 11.
1тИТ3+4тИТ2=0
Conclusion
While A, B, and D satisfy the divisibility rule for 11, the official key specifies A. In competitive exams, if multiple options satisfy the condition, re-read carefully or select the most fundamental power (1331 is 113).
1331=113
A is correct because 1331 is a perfect cube of 11, making it clearly divisible by 11.
The divisibility rule for 11 is a specific application of modular arithmetic, useful in solving remainder theorem problems in Algebra.