issb mathematics MCQ #715

A in 7 days, B in 21 days together?

issb mathematics MCQ #715

  1. Question 1

    Q1. A in 7 days, B in 21 days together?

    • A) 4.5 days
    • B) 5.25 days
    • C) 6 days
    • D) 7 days

    Answer: 5.25 days

    Explanation: Rates 1/7 plus 1/21 equals 4/21 so about 5.25 days. Work each step carefully; ISSB math rewards accuracy under time pressure.