Market sizes and company totals mean millions and billions, and the most common slip in a case interview is a lost zero. A few habits prevent it.
- Split the digits from the zeros. 18 million × 144 is 18 × 144 = 2,592, then put the six zeros back: 2,592 million, about $2.6 billion.
- Use the labels. Thousand × thousand = million. Thousand × million = billion. Million ÷ thousand = thousand.
- Divide by cancelling zeros. 3.6 billion ÷ 1,200 is 3,600 million ÷ 1,200 = 3 million.
- Check the size. Does the answer make sense next to something you know? A company with more revenue than its whole market has a zero problem.
Always say the unit with the number: "about 2.6 billion dollars a year", not "2.6". In the answer boxes you can type 2.6bn, 480k or the full number.