<https://www.studyrankers.com/2018/05/rd-sharma-solutions-class-9th-number-system-6.html>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.studyrankers.com/2018/05/rd-sharma-solutions-class-9th-number-system-6.html>