Question
Evaluate \(20^3 + (-9)^3 + (-11)^3\)
This question was previously asked in
RRB NTPC 2025 Graduate CBT 2 Question Paper PDF (10-Jul-2026) (Shift 1)
The correct answer is
5940
Let \(a = 20,\; b = -9,\; c = -11\).
Check: \(a + b + c = 20 + (-9) + (-11) = 0\).
When \(a + b + c = 0\), the identity states: \(a^3 + b^3 + c^3 = 3abc\).
Applying the identity: \(3 \times 20 \times (-9) \times (-11) = 3 \times 20 \times 99 = 3 \times 1980 = 5940\).
Hence, \(20^3 + (-9)^3 + (-11)^3 = 5940\).
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