Randomly selects a marble

Question

A bag of colored marbles include:

 

6 blue marbles 

4 red marbles

5 black marbles

9 brown marbles

 

Savannah randomly selects a marble and then puts it back into the bag. She does this 12 times. How many times would you expect that she selects a blue marble? Show the calculations you must make

Answer 1

6 blue marbles out of a total of 24 marbles

6/24=1/4

the probability of picking a blue marble is 1/4

this means that for every 4 marbles you choose, chances are that 1 of them will be blue

12/4=3

you would expect to select a blue marble 3 times

another way of looking at the problem...

the probability of picking a blue marble is 1/4 and you pick a marble 12 times; (1/4)*(12)=3