Answer:
33 marbles
Step-by-step explanation:
Given that :
Distribution of marbles :
Blue = 10
Gray = 10
Red = 10
Yellow = 10
In other the be sure that 3 red marbles has been picked ; the fewest number of marbles that must be picked without replacement is :
To be completely sure;
Assume that all blue, yellow and gray marbles are picked first :
(10 + 10 + 10) ;
Then we can be sure that even if no red has been picked among the 30 ; the only remaining marbles are red and picking the next 3 ; means picking 3 red marbles.
Hence, to be completely guaranteed ; the fewest number of marbles that 3 red marbles are picked is :
(10 + 10 + 10 + 3) = 33 marbles