Let us suppose that the interest on the principal of ₹50000 is x.
On principal ₹100, the interest is ₹12.
We shall take the ratio of interest to principal, write it in two forms and obtain an equation.
x50000=12100
x=12100×50000=6000
Therefore, Amount = Principal + Interest
= 50000 + 6000
= 56000 rupees
Hence, Narendra will have to return 56000 rupees to the bank at the end of the year.