Nups1324
1. How were you able to identify that the Y coordinate of Point P is its height or did you just assume.? Or is there a property which says that the X coordinate has to be the Base and the Y coordinate has to be the Height?
I wouldn't even look at this question unless you're near the top end of the Quant scoring scale. You should really be practicing questions that are at or just slightly above your level, and this is a very high-level problem.
When you choose a base for a triangle, you find the triangle's height by:
- extending the base so it is infinitely long (if you need to)
- measuring the perpendicular distance from that infinitely long base to the third point of the triangle
So for triangle APB here, if we decide AB will be our base, we first imagine it is an infinitely long line, so in this diagram, our base becomes the x-axis. Then to find the triangle's height, we want to find the perpendicular distance from point P to the x-axis. That distance will just be the y-coordinate of point P, since we're measuring the distance in a perfectly vertical direction.
Once you know point P is at (x, 3/2), you can then use the coordinate geometry distance formula (twice) to find the perimeter of APB. That distance formula is just based on the Pythagorean Theorem, which is why nick's solution above appears to use Pythagoras. But if you're unfamiliar with how to find distances in coordinate geometry, this is definitely not the first question you should practice - you should do much easier questions than this one first.