This is a resource-allocation/optimization problem: a set of tyres each usable for a fixed total distance can be rotated among the wheels of a vehicle so that the total 'tyre-distance budget' (number of tyres times distance per tyre) is spread evenly across however many wheels are actually in use at any time, maximizing the total distance the vehicle can travel before all tyres are worn out.
Each tyre can be used for a maximum of 90 km before it must be replaced/rotated out. A three-wheeled vehicle carrying one spare has 4...
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