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SAT Math Videos 171 videos
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SAT Math 3.2 Statistics and Probability 195 Views
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Description:
SAT Math 3.2 Statistics and Probability
Transcript
- 00:02
Here’s your shmoop du jour, brought to you by Marbles.
- 00:06
If found, please return to… oh, we can’t even remember where.
- 00:10
A bag contains yellow, blue, and red marbles.
- 00:13
The probability of drawing a red marble is 1/4 and the probability of drawing a yellow marble is 3/5.
- 00:19
If there are 100 marbles in the bag, how many are blue?
Full Transcript
- 00:23
And here are the potential answers…
- 00:26
To solve this problem, we just have to figure out what fraction of marbles are blue.
- 00:31
Okay, we’re given the probability of drawing a red and yellow marble, so we can figure
- 00:35
out how many red and yellow marbles are in the bag.
- 00:37
We start with 100 marbles. 1/4 of them are red.
- 00:41
To find how many marbles that is, we just have to find 1/4 of 100.
- 00:44
That’s easy, multiply the two, and voila, that’s it.
- 00:47
25 marbles are red.
- 00:49
Now for yellow. The problem tells us that 3/5 of them are yellow.
- 00:54
Again, we multiply 3/5 times 100 and we get 60.
- 00:58
Since there are 25 red marbles and 60 yellow marbles and all the rest are blue....
- 01:04
...we get 25 plus 60 is 85.
- 01:08
Then, just subtract that 85 from 100, and we get 15 are blue.
- 01:12
So our answer is (B).
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