Solution : Given data : Distance covered = 385 km Time for the whole journey = 7 hours Stoppage time = 7 × 5 ⇒ 35 minutes Fuel consumption of bike = 1ml/minute/10 (km/hr) Diameter of fuel injector = 2 mm = 0.2 cm Radius of cylindrical Fuel tank = 14 cm Part of fuel used = 30% Formulae and Concept used : Distance = Velocity × time Volume of cylinder = π × r2 × h 1 ml = 1 cm3 Calculation : Distance covered = 385 km Actual time = (7 × 60) – 35 ⇒ 420 – 35 ⇒ 385 minutes Average speed = Distance/Time ⇒ 385/(385/60) ⇒ 60 km/hr Fuel used, 1 ml for 1 minute for 10 km/hr ⇒ 6 ml for 1 minute for 60 km/hr ⇒ (6 × 385) ml for 385 minutes for 60 km/hr ⇒ Fuel used = 2310 ml = 2310 cm3 This fuel comes from injector into the engine with the rate of v (cm/minute) Volume of tube = π × r2 × v × t (in minutes) ⇒ (22/7) × (0.2/2) × (0.2/2) × v × 385 = 2310 ⇒ v = (2100/11) cm/min = (21/11) m/min Amount of fuel used is 30% of the fuel tank so, Volume of tank = π × r2 × l ⇒ (22/7) × (14/2) × (14/2) × l × (30/100) = 2310 ⇒ l = 50 cm ∴ Fuel is injected into the tank at the rate of 12/11 m/min and length of the cylindrical fuel tank is 50 cm.