If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

# Dilating shapes: expanding

Sal is given a rectangle on the coordinate plane and he draws the image of the rectangle under a dilation with scale factor 1 2/3 about an arbitrary point. Created by Sal Khan.

## Want to join the conversation?

• I get almost all the video, but this one part confuses me. At , where did Sal get the 3 to minus the 10 with?
• Point P is located at (-7,3) and the dilation needs to be 10 away from that. The 3 is the y-coordinate of the original point, so Sal subtracted the 10 from the positive 3 to get -7, the y-coordinate of the new point.
• How do you do a dilation when the scale factor is a percentage?
• you could make it into a decimal by dividing by 100 and then use that instead of the percentage. From that, it is basically the same as the video.
Hope it helps!
• It's not hard. You just find the original line segment and then you multiply it by the scale factor. Just do that for all 3 sides. Then you get your new triangle!
• Is there a formula for this?
• if you're dilating about the origin then multiply all points' coordinates by however much you're dilating by yes?
• the problems on the practice are all triangles so this example that is being shown is not very helpful because triangles have a center that you have to account for and most of the triangles I had to do were off-centered/crooked which made it much harder..... just saying this video would be way more helpful if it included more shapes
• Rather than thinking of it as a triangle, think about having to move three points from the center. Each point has a horizontal and vertical distance from the dilation point, so whatever the scale factor is, multiply each part by the scale factor to find where the prime point should go. Do this three times, and you have the right answer. The prime points should be co-linear with their vertex point and the center of dilation. The shape does not matter as long as you do all the vertices the same way,
• Does anyone know a easier way to do this?
• Well, if you have a square, its very easy, just find the difference between the line segments, and because all the sides are the same so you just have to plot out the shape. But if you do this on a rectangle it's the same steps it just takes longer.
(1 vote)
• At , if the base shape is a triangle in which its sides and points are not on the marks of the graph, how do you expand the shape? Please help!
• Can u make the whole video more clear