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CAHSEE Math 3.4 Mathematical Reasoning 180 Views
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Description:
CAHSEE Math: Mathematical Reasoning Drill 3, Problem 4. Which of the expressions gives the best estimate as to the length of this quadrilateral's perimeter?
Transcript
- 00:03
Shmoop, there it is… Shmoop, there it is...
- 00:08
A quadrilateral has sides measuring 24.27 cm, 12.39 cm, 9.75 cm, and 25.99 cm.
- 00:18
Which of the following expressions gives the best estimate as to the length
- 00:21
of this quadrilateral's perimeter?
- 00:23
Here are the potential answers…
Full Transcript
- 00:30
Ok, what is this question asking?
- 00:32
Well yeah, it’s testing our mad rounding skillz…
- 00:35
…but it’s also testing to make sure we can avoid traps.
- 00:39
We should note that our four answer choices apparently went to… 4 very different schools.
- 00:44
“A” rounds up or down to the nearest 10.
- 00:47
B SOMETIMES rounds up, sometimes down, sometimes to the nearest 1, sometimes to the nearest 10...
- 00:54
…and so on. They’re all over the map. In that case, we need to pay attention to
- 00:58
how far away we’re getting from the original number.
- 01:01
A goes down about 4, then down 2, the up almost nothin’, then up 4.
- 01:06
All told, A is only about 2 off the correct total. Not bad.
- 01:10
What about B? Down 4, down almost nothin’, up almost nothin’, and down 6.
- 01:16
Combined, off by 10 or so. No good. C is down 4, down 2, up almost nothin’,
- 01:22
up almost nothin’. Down 6 all day. A is still in the clubhouse with the lead…
- 01:27
Finally, D. Up 6, up almost nothin’, up almost nothin’, down 6.
- 01:32
There are some pretty big swings in there… but at the end of the day, it’s pretty spot on.
- 01:36
Our answer is D.
- 01:37
As in, “Duffer.”
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