The Brainliest Answer!
Let the dimensions of the cuboid container be x,y and z
Thus, volume of cuboid is xyz
According to the question, in a cuboid of volume xyz, 100 boxes can fit.

Now the increased dimensions of the container when doubled = 2x, 2y and 2z
Thus, volume of larger container = 2x * 2y * 2z
= 8xyz

So, we find that when the dimensions of the container is doubled, the volume increases 8 times. Therefore the number of boxes it can hold will also increase to 8 times
Thus, no. of boxes it can hold = 100 x 8 
= 800 boxes

Hope that helps !! 
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Let dimesnsion be x
= 2x+2x+2x = 8x
now  the voume increases 8 times the capacity of it will be also 8 times then,
8*100= 800 boxes