Query about Question 9 from "10 Medium Quant Questions - March 2, 2023" [2399]

GRE GRE Quant Problem Solving
1

https://www.gregmat.com/quizzes/quiz/10-medium-quant-questions-march-2-2023 (Question 9)

I dont understand how come we reached 120/root 3

2

Kindly refer to below link.

30-60-90 Triangles