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:
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
Discussion & Comments