 
<translate> Speed ala mmiri = d/t = 90/(2 1/2) = 36 kmph Speed elu mmiri = d/t = 45/(2 1/2) = 18 kmph The ọsọ nke iyi = (36 - 18) / 2 = 9 kmph N'ihi ya, azịza ya bụ (A). <eng> Speed downstream = d/t = 90/(2 1/2) = 36 kmph
Speed upstream = d/t = 45/(2 1/2) = 18 kmph
The speed of the stream = (36 - 18)/2 = 9 kmph
Therefore, the answer is (A). 