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SAT Math 9.1 Geometry and Measurement 261 Views


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SAT Math 9.1 Geometry and Measurement

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English Language

Transcript

00:02

Here’s your shmoop du jour, brought to you by parallelograms.

00:06

The Leaning Tower of Pisa of rectangles.

00:11

Given that ABCD is a parallelogram, find the value of y.

00:17

Here are the potential answers...

00:19

Well, we’re really only given one piece of information, other than in the diagram…

00:24

…which is that we’re looking at a parallelogram.

00:27

We know a few things about parallelograms…and one of those things is going to help us a ton here.

00:32

Opposite sides of a parallelogram are always equal in length.

00:39

That tells us that 6x – 6 = 4x + 5…

00:43

…and 8y + 3 = x – 5.

00:47

We’ll start with the first one so we can nail down the value of x.

00:50

Watch your fingers.

00:51

If we subtract 4x from both sides…

00:54

…and add 6 to both sides…

00:55

…we get 2x = 11.

00:58

Dividing both sides now by 2, we see that x = 11/2.

01:04

Now we can take that value and throw it into our other equation…

01:07

…which becomes 8y + 3 = 11/2 – 5.

01:11

5 can be rewritten as 10/2…and 11/2 minus 10/2 is just… 1/2.

01:19

We can subtract 3 from both sides to get 8y = -2 1/2.

01:23

When dividing both sides by 8, we may want to rewrite that part on the right as -5/2,

01:29

to make things easier.

01:31

-5/2 divided by 8 is the same as multiplying it by 1/8…

01:36

…which comes out to -5/16.

01:38

Answer C.

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