The cube of which number among the following is a 7-digit number?

50³ = 125000 (6 digits). 99³ = 970299 (6 digits). 100³ = 1000000 (7 digits). 200³ = 8000000 (7 digits). Among the options, 200³ is clearly a 7-digit number. (100³ also is, but the question asks which 'is'; 200 is also valid and listed.) Actually 100³ = 1,000,000 — that's 7 digits too. Both 100 and 200 yield 7-digit cubes. Convention: if both options give 7-digit answers, the question is ambiguous — but 200³ = 8,000,000 is the more clearly 7-digit answer.