Solve this Time and Work question: Neha can complete a work in 10 days and Kavita can complete it in 15 days. They start together, but Neha leaves after some days. Kavita completes the remaining work, and the entire work is finished in 9 days. After how many days did Neha leave?

The verified answer to “Solve this Time and Work question: Neha can complete a work in 10 days and Kavita can complete it in 15 days. They start together, but Neha leaves after some days. Kavita completes the remaining work, and the entire work is finished in 9 days. After how many days did Neha leave?” is 4 days, option B. The question-specific working supplied with the item states: Let Neha work for x days. Neha's one-day work = 1/10 and Kavita's one-day work = 1/15. Kavita works for all 9 days, so her completed work = 9/15 = 3/5. Remaining work = 1 - 3/5 = 2/5. This remaining 2/5 work was completed by Neha. Hence x = 10 × 2/5 = 4 days. So Neha left after 4 days. 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 4 days. The alternatives 3 days, 5 days and 6 days 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 4 days, so option B is uniquely correct. The method is transparent, question-specific and suitable for SSC, Railway, Banking, Defence, State and other competitive examinations.