Two persons Kuldeep and Agarkar can reap a field in 8 and 12 hours respectively. They work in alternate one-hour shifts, with Kuldeep starting at 9 a.m. When will the reaping finish?

1. Rates: Kuldeep 1/8 per hour, Agarkar 1/12 per hour; a 2-hour cycle does 1/8 + 1/12 = 5/24. 2. After 4 cycles (8 hours, up to 5 p.m.): 4 × 5/24 = 20/24 done, leaving 4/24. Hour 9 (Kuldeep) adds 3/24 → 23/24 at 6 p.m., leaving 1/24. 3. Agarkar does 1/24 in (1/24)÷(1/12) = 0.5 hour, finishing at 6:30 p.m. _Source: RRB Group D CEN-02/2018 PYQ, Q.52._