Çözüldü Probability of "Mutually Exclusive" (Disjoint) Events

A certain experiment has three possible outcomes. The outcomes are mutually exclusive and have probabilities p, p / 2, and p / 4, respectively. What is the value of p?
https://www.ets.org/s/gre/pdf/practice_book_GRE_pb_revised_general_test.pdf
(Sayfa 79, Test 5, Soru 23, Cevaplar sayfa 114)
(ets.org sitesinden silinmiş.)

p + p / 2 + p / 4 = 1 ⇒ p = 4 / 7

Reference: https://www.mathsisfun.com/data/probability-events-mutually-exclusive.html