Final answer:
The scale factor k for the dilation mapping X onto Y is 1.5, which indicates an enlargement since k is greater than 1.
Step-by-step explanation:
To find the scale factor k for the dilation mapping point X onto point Y, you can use the ratio of the distance from the center C to Y over the distance from the center C to X. In mathematical terms:
k = CY / CX
In this problem, CY = 15 and CX = 10. Therefore:
k = 15 / 10 = 1.5
This means that the scale factor is 1.5. Since k is greater than 1, the dilation is an enlargement, because the image Y is larger than the pre-image X by a factor of 1.5.