Hi! So if you know the probability of choosing a red marble in that given jar is 1/4, you can then figure out what the probability of not choosing a red marble, or choosing a blue marble, is. That probability would be called the complement of 1/4, and what would be added to it to make 1. In this case, it would be 3/4. Since 27 of the marbles are blue, and the chance of drawing a blue marble is 3/4, we can then say 27 = 3/4 of the jar. Now the easier way is to find what 1/4 then equals and add it up. Since 1/4 is 1/3 of 3/4, we can see what 1/3 of 27 is to find what 1/4 of the marbles in the jar is. 1/3 • 27 = 9. So if we add 9 and 27 together, that's the total number of marbles in the jar. 27 + 9 = 36. There are 36 marbles in the jar.
Yes, use the methods you have learned like the proportional probability method and plug in the values you are trying to solve to help in the real world! Hope this helps!
