A number divided by 11 leaves a remainder 3. What is the remainder when the square of the same number is divided by 11?

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  1. 7
  2. 5
  3. 9
  4. 11

Answer (Detailed Solution Below)

Option 3 : 9
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यूपी पुलिस SI (दरोगा) सामान्य हिंदी मॉक टेस्ट
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Detailed Solution

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Given:

A number divided by 11 leaves a remainder of 3.

Formula used:

Let the number be n. Then, n = 11k + 3 for some integer k.

We need to find the remainder when \(n^2\) is divided by 11.

Calculation:

\(n^2\)\((11k + 3)^2\)

\(n^2\)\(121k^2 + 66k + 9\)

⇒ \(n^2 \mod 11\)\((121k^2 + 66k + 9) \mod 11\)

⇒ \(n^2 \mod 11\)\((0 + 0 + 9) \mod 11\)

⇒ \(n^2 \mod 11\) = 9

∴ The correct answer is option (3).

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