Opposite sides of a rectangle are congruent
10 + 2x = 18
2x = 18 - 10
2x = 8
x = 8/2
x = 4
The area ratio is 1:16 meaning that the old area is 1 while the new area is 16. So this is another way of saying "the area is multiplied by 16"
Take the square root of each part of the ratio of 1:16 and we get 1:4
So this is the scale factor. It tells us how the linear components of the circles relate to one another. If the circumference of the smaller circle is 1,then the larger circle has a circumference of 4.
Therefore, the circumference has been multiplied by 4
