WAEC Mathematics 2014 Theory — Question 6
Question 6 of 23 from the West African Examinations Council (WAEC) Mathematics 2014 Theory paper, with the correct answer and a full explanation.
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3(b). A man drives from Ibadan to Oyo, a distance of 48km, in 45 minutes. If he drives at 72km/h where the surface is good and 48km/h where it is bad, find the number of kilometers of good surface.
Model answer
Let d = distance of good surface, so (48−d) = distance of bad surface. Time = distance/speed. Total time = 45min = 0.75h. d/72 + (48−d)/48 = 0.75 Multiply through by 144 (LCM of 72,48): 2d + 3(48−d) = 108 2d+144−3d=108 −d=−36 d=36km
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