Each dog consumes 250 grams x 2 = <<250*2=500>>500 grams of dog food each day.
So, 4 dogs consume 500 grams x 4 = <<500*4=2000>>2000 grams of dog food each day.
Since there are 1000 grams in 1 kilogram, then the 4 dogs can consume 2000/1000 = <<2000/1000=2>>2 kilograms of dog food each day.
Aunt Gemma bought a total of 50 kilograms x 2 = <<50*2=100>>100 kilograms of dog food.
Hence, it will last 100 kilograms/2 kilograms = <<100/2=50>>50 days.
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