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Question

Which of the following numbers is a perfect square?

The correct answer is
48841

Identifying Perfect Squares Using Number Properties

To determine if a number is a perfect square, we can use two main methods: checking the last digit and calculating the square root.

Last Digit Rule Analysis

Perfect squares have specific last digits. A perfect square cannot end in 2, 3, 7, or 8.

Let's examine the last digit of each option:

  • 48841 ends in 1 (Possible perfect square)
  • 58287 ends in 7 (Cannot be a perfect square)
  • 68763 ends in 3 (Cannot be a perfect square)
  • 38262 ends in 2 (Cannot be a perfect square)

Only 48841 passes this initial check.

Square Root Verification

Now, we verify if 48841 is indeed a perfect square by calculating its square root.

Estimate the square root:

  • We know that $200^2 = 40000$ and $250^2 = 62500$. Therefore, the square root of 48841 lies between 200 and 250.
  • Since 48841 ends in 1, its square root must end in 1 or 9.

Let's test the number 221:

Using LaTeX for calculation:

$ 221^2 = 221 \times 221 $

$ 221 \times 221 = 48841 $

The calculation confirms that $221^2$ equals 48841.

Final Answer

The number 48841 is a perfect square because its square root is an integer (221).

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Important Questions from Number System (Notes)

  1. Which number system uses only digits 0 and 1?
  2. The sum of the digits of a 2-digit number is 12. When the digits of the number are interchanged, the number becomes 15 more than twice the original number. The original number is:
  3. What is the least number which, when divided by 7, 12 and 15 leaves 1 as the remainder in each case?
  4. If $\frac{1}{9!} + \frac{1}{10!} = \frac{x}{11!}$, then the value of x is:
  5. What will be the output, if we compute the 9's complement of the decimal number 782.54?
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