A chance to use algebra! Each bag containts .5 cubic feet (cu. ft.) X = Number of bags X*0.5 cu. ft. = 600 cu. ft. X = 600 cu. ft./0.5 cu. ft. X = 1200 Bags
2in=0.1667ft, so 0.1667*1100=183.37 cu ft. You'll need 183.37÷0.5~367 bags.
.5 cu ft x 25 equals, do the math.
Yes, if you do not put a tarp down first.
Each bag covers .5 cu ft. Their for .5x400 equal do the math.
No, only lava rocks can be used.
There are 64 bags to a pallet
If you are going to use the marble around (not covering) plants already growing, they would be nice. Just remember these chips can be up to 1" and are heavier than garden "pebbles". Also, rinse the chips first to get rid of the marble dust.
They are good at keeping weeds out, but I don't know that it would help keep out bugs. There are probably fewer bugs with this than open soil, and I haven't seen any bug problems since I installed the marble chips.