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.
The process that occurs when physical forces break rock into smaller pieces without changing the rock's chemical composition is called mechanical weathering.
Name the scientific Advisor to the Defence Minister and DRDO's DG (Missiles & Strategic Systems) who has won the first IEI-IEEE Award for Engineering Excellence - 2015 in recognition of his significant national contributions towards missiles and aerospace technologies.