Answer:
The difference between the A300 & the A340 is that:
-The A300 has two engines, A340 has Four '4 engines 4 long hual'
-The A300 is a short to medium range aircraft, while the A340 is a long range aircraft, from Newark in the USA to Singapore. 18 hours non stop.
-The A300 is significantly shorter than the A340. It can nearly be double the length.
-Airbus has ceased the A300 production line as of 2007 but the A340 production line is still going.
-Can seat up to 300 persons. The A340 can carry up 380 in three class layout.