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LPG contains butane and propane both.  If there is a choice to be made, then Butane.
Liquefied petroleum gas is produced from petroleum.  It consists of propane C3H8 or butane (C4H10) or a mixture of both.  It depends on the countries and suppliers in what proportion they are mixed.  Butane propane and air are mixed in commercial LPG.

If we are talking of LPG for cooking, butane is more efficient as it burns at higher temperature and lasts longer.  Propane is not so efficient.

Methane is the natural gas that is used in some other applications.  Its calorific value is much less than that of butane or propane.

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the main constituents of lpg are butane and propane.
                                                                                    plz mark it best
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