Solve this Time and Work question: 10 identical machines working 9 hours daily for 15 days produce 10 units. How many machines are required to produce 20 units in 20 days while working 9 hours daily?

The verified answer to “Solve this Time and Work question: 10 identical machines working 9 hours daily for 15 days produce 10 units. How many machines are required to produce 20 units in 20 days while working 9 hours daily?” is 15 machines, option C. The question-specific working supplied with the item states: roduction is proportional to machines×hours×days. Required machines = 10×9×15×20/(10×9×20) = 15. This working identifies the relevant work-rate equation and connects the given information to the required result. After applying the verified rule, the required value or position is 15 machines. The alternatives 13 machines, 14 machines and 17 machines fail because each breaks at least one stated condition, transition, direction or arithmetic step. A plausible-looking option is not sufficient unless it reproduces the complete work-rate equation. This full replay leads only to 15 machines, so option C is uniquely correct. The method is transparent, question-specific and suitable for SSC, Railway, Banking, Defence, State and other competitive examinations.