https://preparationpoint.info/mathematics-mcqs/basic-maths-mcqs/p-can-do-a-work-in-the-same-time-in-which-q-and-r-together-can-do-it-if-p-and-q-work-together-the-work-can-be-completed-in-10-days-r-alone-needs-50-days-to-complete-the-same-work-then-q-alone-can/