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Question

John runs 25% faster than Ahcène. Ahcène runs 25% faster than Paul. Together they run a relay in which each one of them runs 1 km. If, together, they took 10 minutes to run these 3 km, what was the average speed of Ahcène in km/h ?

(A) 6.1 (B) 18 (C) 18.3 (D) 36 (E) 36.6

Answer 1

The trick here is to remember that distance divided by rate = time Let P = Paul's rate, then Achene's rate is 5P/4 and John's rate is 25P/16 1/(25P/16) + 1/(5P/4) + 1/P = 10 Multiply by P and simplify the fractions 16/25 + 4/5 + 1 = 10P Simplify the fraction further 61/25 = 10P P = 61/250...but this is in km/min...convert to km/hr by multiplying by 60 min/hr P = 366/25 km/hr = 14.64 km/hr A = P*5/4 =18.3 Nasty fractions!!!!!