Square-root equation with an unknown addend: If √(75.24 + N) = 8.71, determine the value of N.

Difficulty: Easy

Correct Answer: .6241

Explanation:


Introduction / Context:
We are reversing a square-root operation to recover the missing addend inside the radical. This is a standard technique in quantitative aptitude involving squaring both sides carefully.


Given Data / Assumptions:

  • √(75.24 + N) = 8.71.
  • All quantities are decimal reals.
  • No approximation is required beyond exact decimal squaring.

Concept / Approach:
Square both sides to eliminate the square root, then isolate N. The arithmetic requires precise decimal squaring of 8.71.


Step-by-Step Solution:

Square the right-hand side: 8.71^2 = 75.8641.Thus, 75.24 + N = 75.8641.N = 75.8641 − 75.24 = 0.6241.

Verification / Alternative check:
Check: 75.24 + 0.6241 = 75.8641 and √75.8641 = 8.71 exactly.


Why Other Options Are Wrong:

  • 6.241 and 62.41 are off by factors of 10 or 100.
  • “None of these” is incorrect because 0.6241 is listed.
  • 0.06241 is a decimal-place error.

Common Pitfalls:
Mis-squaring 8.71 or mishandling decimal subtraction can lead to place-value mistakes.


Final Answer:
.6241

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