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SAT Math 3.2 Statistics and Probability 195 Views


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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?

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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