Rs.4000/- amounts to Rs.5,000 in 8 years, in what time will rs.2,100/- amount to Rs.2,800/- at the same rate?

From Rs. 4000 to Rs. 5000 i.e. the increment of Rs. 1000 takes 8 years. 
We need to find out the time taken for the increment of Rs. 700 i.e. Rs. (2800 - 2100)?

 

For Rs. 1000, the time taken for increment = 8 years.

Hence, for Rs. 700, the time taken for increment will be: [8/1000 x 700] 

 

On solving the above equation, we get the time to be 5.6 years.