Evaluate [(2.39)<sup>2</sup> − (1.61)<sup>2</sup>] ÷ (2.39 − 1.61).
Aptitude
Decimal Fraction
Difficulty: Easy
Choose an option
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A4.00
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B3.90
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C4.10
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D3.78
Answer
Correct Answer: 4.00
Explanation
Problem restatementSimplify a difference of squares divided by the corresponding difference.
Concept/ApproachUse a2 − b2 = (a − b)(a + b). Dividing by (a − b) leaves (a + b).
Step-by-Step calculation[(2.39)2 − (1.61)2] ÷ (2.39 − 1.61) = 2.39 + 1.61= 4.00
Verification/AlternativeDirect computation of squares is unnecessary once the identity is recognized.
Common pitfallsExpanding both squares numerically instead of applying the identity.
Final Answer4.00