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Interview prep / Brainteaser/Logic

Cubing fifteen in your head

Question

Without writing anything down, find 15315^3.

Short answer

3375. 152=22515^2=225 and 225×15=2250+1125=3375225\times15=2250+1125=3375.

Adapted from Joshi, Denson & Downes, Quant Job Interview Questions and Answers, Q8.2, p.276; question and answer rewritten by SelfMadeQuant.com.

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