Foreign carmakers have been slashing the prices of petrol-powered cars they make in China by more than 20 per cent to survive in a cutthroat market amid weakening consumer demand.Last month, big international marques including Volkswagen and Toyota offered average discounts of 23.4 per cent on cars powered by internal combustion engines, according to data from the China Passenger Car Association (CPCA). That compared with an average discount of 23.7 per cent in July.“Because their new cars...