https://preparationpoint.info/solved-past-papers-mcqs/ppsc-past-papers/ppsc-past-papers-2018/provincial-management-service-etc-bs-17-general-knowledge-2018/if-a-completes-a-job-in-20-minutes-and-b-in-30-minutes-if-they-do-the-same-job-togather-how-much-time-will-they-take/