A) 24 km (Upstream) + 36 km (Downstream) → 8 hrs 30 min →

**1**

36 km (Upstream) + 24 km (Downstream) → 9 hrs → 2

1.5 * 2

9hrs*1.5 = 13.5 hr i.e 13 hr 30 min

54 km (Upstream) + 36 km (Downstream) → 13 hr 30min → 2

30 km (Upstream) → 5 hrs.

→ Upstream speed = 30/5 =

**6 kmph**

From here How to proceed?