(3) Speed of current = x kmph.Rate downstream of boat B= (10 + x) kmph Speed of boat A in still water= (10 + x) kmph ∴ Rate upstream= 10 kmph According to the question,
40
10
−
24
10x
=2 ⇒
24
10+x
=4–2=2⇒10+x=12 ⇒ x = 2 kmph ∴Speed of boat A in still water = 10 + 2 = 12 kmph