rule of thumb:
A 320 40 kg/min
A 330 90 kg/min
A 340 140 kg/min
Widebody/Long Haul aircraft have varying fuel flows, depending on their weight. TO weight can easily be twice as much than for landing. That's because they carry a big percentage of their weight as fuel.
That's why on wide bodies, you never have figures like these. The correct answer is: average fuel consumption is fuel burn divided by flight time (for a specific flight).
Even for a guesstimate as holding fuel at your destinations your numbers don't add up, the 340 figures resemble more of those of a A340-500/600. A 340-300 uses about 90 kg/min. The magic figure is 2.8 tons (30 min final reserve) vs 4.2 tons for a A340-500.