Arithmetical Reasoning: A boat goes 20 km downstream in 2 hours and 12 km upstream in 3 hours. Find the speed of the boat in still water and the speed of the stream.

Let the speed of boat in still water = x km/hLet the speed of stream = y km/h

Downstream speed = (x + y)Upstream speed = (x – y)

Condition 1: 20 km in 2 hours → (x + y) = 20 ÷ 2 = 10Condition 2: 12 km in 3 hours → (x – y) = 12 ÷ 3 = 4

Now solve:x + y = 10 …(i)x – y = 4 …(ii)

Add (i) and (ii): 2x = 14 → x = 7Substitute in (i): 7 + y = 10 → y = 3

Answer: Speed of boat in still water = 7 km/h, Speed of stream = 3 km/h