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SAT Math Videos 171 videos

SAT Math 1.1 Algebra and Functions
315 Views

SAT Math 1.1 Algebra and Functions. Find an algebraic equation to correspond with the data.

SAT Math 1.1 Geometry and Measurement
719 Views

SAT Math 1.1 Geometry and Measurement. What is the circumference of the circle?

SAT Math 1.1 Numbers and Operations
280 Views

SAT Math 1.1 Numbers and Operations. How many combinations of beverage and cereal can be made?

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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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