 
<translate> Ntụgharị uche: Obosara nke ọdọ mmiri ahụ bụ 4 * 15 = 60 kilomita. Ọ na-egwu mmiri n'ọsọ 60 / 20 = 3 mph. Ya mere, ọ na-eji ọsọ nke 3 * 2 = 6 mph. Nke ahụ pụtara na ọ na-ewe ya awa 60 / 6 = awa 10 ịkwọ ụgbọ gburugburu ọdọ mmiri ahụ. <eng> Reasoning: The perimeter of the lake is 4 * 15 = 60 miles. He swims at a speed of 60 / 20 = 3 mph. So he rows at a speed of 3 * 2 = 6 mph. That means it takes him 60 / 6 = 10 hours to row around the lake. 