Answer: 0.089
Step-by-step explanation:
Number of combinations of n things taking r at a time :-
Given : A box has eight green marbles, five red marbles, and seven blue marbles.
Total marbles = 5+8+7=20
We choose three marbles from the box at random without looking.
Number of ways to choose 3 marbles with same color :-
(1)
Total ways to select 3 marbles from 20 marbles :-
(2)
Now, the required probability (divide (1) by (2)):-
Hence, the required probability : 0.089