The correct option is C 768
The dimensions of a plank are
Length, l=5 m=500 cm,
Breadth, b=25 cm,
Height, h=10 cm,
We know that,
Volume of the plank = l×b×h
= 500×25×10 = 125000 cc
The dimensions of the pit are
Length, l=20 m=2000 cm,
Breadth, b=6 m=600 cm,
Height, h=80 cm,
We know that,
Volume of the pit = l×b×h
= 2000×600×80 = 96000000 cc
Also, note that the length of the pit is a multiple of the length of a plank. The same holds true for other two dimensions. In such a case:
The number of planks that can be stored = Volume of the pit/Volume of a plank = 96000000/125000 = 768