The age of the father 4 years ago was 8 times the age of his son. At present, the father's age is 4 times that of his son. Find the present age of son.
As per the data released by the IncomeTax Department in December 2017, how much percent of total population paid income tax in the assessment year 201516?
If quantity of good X demanded increases from 4000 units to 5000 units when price of good Y increases from Rs 75 to Rs 90, find Arc Cross elasticity of demand?