The table provided displays the estimated cost (in ₹ lakh) for the construction of a canal between two points.
Based on the information in the table, answer the questions that follow.
If the length of the canal to be laid each year is proportional to the estimated cost for materials and labour, what fraction of the total length is intended to be completed by the third year?
First, let us note down the table and find out the sum of the costs across the rows and columns: