ACT Math: Find The Perimeter Of A Figure

The purpose of education is to learn to think critically. In this problem you have to spot something that others would miss. Here's the problem. All right angles. Dimensions given in inches. Find the perimeter in inches. This problem is challenging, because not all lengths are given and you have to first recognize that they aren't all shown and then derive them from the information given. On the left we have an unknown length, but we have enough information to derive the length of that side. On the right notice that 2 + 1 + 3 = 6. So we write 6 for the left side. The mistake kids make on the ACT is they just count the numbers shown, get 27 and go to the answers and look for 27, but it's not there. To get this one right, you must recognize that three lengths are not marked, so how can you add up the sides to get the perimeter? We have a side marked 12 at the bottom
On top, one marked 3, but two others not indicated. What is their length. Together they are 12 - 3 = 9. Is it necessary to know more about these two sides?
If we called one x the other would be 9-x. Add them together and get 9 - x + x = 9. So just use 9 for those two lengths. That's all you need. The SAT clock is ticking
We're asked for the perimeter, so let's just use 9 as the lengths of those two sides. We don't need to resolve the length of each. Together, they are 9. We have accounted for all sides. Now we are ready to add them up. Starting at the bottom and going clockwise we have
12 + 6 + 3 + 3 + 9 + 1 + 2 = 36 The correct answer is C

I like to tutor, as I did in college, but I no longer need the money
In the first hour of this video, 50 people saw it
At 3 min each, that's 150 minutes of tutoring in just one hour and this video can remain up for years, so look at the value created in the time it took to make this video
I think everyone should contribute their time to help kids learn critical thinking
Thanks for watching