Each side of a square land of our village is 300 meter. We shall fence that square land by 3dcm. wide wall with same height around its four sides. Let us see that how much will it cost for the wall at the rate of Rs. 5, 000 per 100 sq. meter.
Area of wall = Area of outer square – Area of inner square
Length of outer square = 300 + 0.3m (3dcm = 0.3m)
= 300.3m
We know, area of square = (side)2
Area of outer square = 300.32 = 90180.09m2
Area of inner square = 3002 = 90000m2
Area of wall = 90180.09 – 90000 = 180.09m2
Rate per square metre of wall = 
= Rs. 50/sq m
So for 1 m2 - - - - Rs. 50
180.09m2 - - - Rs. 50 × 180.09 = Rs. 9004.5
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