In the following question, select the odd number from the alternatives given below. Check whether each number has a special property (such as being a perfect square). Identify the number that does NOT share that property with the others. (A) 361 (B) 441 (C) 784 (D) 876 (E) 1024

Difficulty: Easy

Correct Answer: 876

Explanation:


Introduction / Context:
This odd-one-out problem checks number properties, most commonly perfect squares. A perfect square is an integer that can be expressed as n*n for some whole number n. The odd number is the one that cannot be written as a square, while the others can.


Given Data / Assumptions:

  • A number is a perfect square if it equals n*n for some integer n.
  • We test each option by recalling common squares or checking nearby squares.
  • If several numbers are exact squares and one is not, that one is the odd choice.


Concept / Approach:
Recognize perfect squares by memory (like 19^2, 21^2, 28^2) or by checking whether the number lies exactly on a square boundary. Non-squares will fall between two consecutive squares.


Step-by-Step Solution:

361 = 19*19, so 361 is a perfect square. 441 = 21*21, so 441 is a perfect square. 784 = 28*28, so 784 is a perfect square. 1024 = 32*32, so 1024 is a perfect square. 876: nearby squares are 29^2 = 841 and 30^2 = 900. Since 876 is between 841 and 900, it is not a perfect square.


Verification / Alternative check:
Another quick check is to compute the integer square root estimate. Since 29^2=841 and 30^2=900, any number between them is not a square. Because 876 lies strictly between these, it cannot be expressed as n*n for an integer n. Hence it is the odd one out.


Why Other Options Are Wrong:

361: equals 19^2, so it follows the perfect-square property. 441: equals 21^2, so it follows the perfect-square property. 784: equals 28^2, so it follows the perfect-square property. 1024: equals 32^2, so it follows the perfect-square property.


Common Pitfalls:
A common mistake is assuming any even number is not a square or any number ending in 1 is a square. Another mistake is checking only the last digit. Always confirm by matching to an exact integer multiplication (n*n) or bounding between consecutive squares.


Final Answer:
876

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