Brain Teasers & Mental Math
A stock falls 50%, then rises 50%. Where does it end up versus the start?
Model answer
Down 25% from the start.
Start at 100. Fall 50% → 50. Rise 50% of 50 → 50 × 1.5 = 75. So 75 vs 100 = a 25% loss.
Key insight: percentage gains and losses are not additive…
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