A bowl contains red marbles and green marbles. Sue knows there are 150 red marbles. After mixing the marbles, she randomly selects 50 marbles, 15 of which are red. Approximately how many total marbles are in the bowl?
Assuming that the ratio of red to green marbles is the same in the sample selected (50) as in the bowl.
In the sample, 15 out of 50 are red. i.e. fraction of red marbles =
Totally there are 150 red marbles. If this is also 3/10 of the total marbles in the bowl, and assuming total marbles are x, we get an equation
So there are approximately marbles in the bowl.
Hope this helps.