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    Mental Math & Quick Calculations · Interview Question

    A company has a 12% market share in a $45B market. What is its revenue?

    How to answer

    12% of $45B: 10% of $45B = $4.5B. 2% of $45B = $0.9B. Total = $4.5B + $0.9B = $5.4B. To cross-check: 12% = 12/100. $45B x 12 = $540B. Divide by 100 = $5.4B. Either method works; pick whichever feels faster. In a case, if you are given revenue and market size, you can reverse-engineer market share: $5.4B / $45B = 12%. Being fluent in both directions—share to revenue and revenue to share—is essential.

    Key idea: Break 12% into 10% + 2%.

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