Ones vs Tens

Counting favorable outcomes in a digits comparison probability problem

This is a medium-difficulty probability question that tests your ability to enumerate outcomes systematically and count them accurately. Rather than relying on formulas, it rewards careful case analysis over a well-defined sample space.

To solve problems of this type, you need to first identify all valid two-digit numbers and their structure, then determine which outcomes satisfy the constraint. The key is organizing your count so you don't miss cases or double-count. Quant interviewers use these questions to see whether you can move confidently from a word problem into a rigorous enumeration, and whether you catch the boundaries of the problem (for instance, whether zero plays a role).

• Sample space definition and size
• Systematic case breakdown
• Distinguishing tens and units places