What is the scale factor from ABC to DEF?

The answer to this question is 3. Since triangles ABC and DEF are both similar figures, that means that theire corresponding sides are in fact proportional. Scale factor is the number that you can multiply by in order to decrese or incrrease the size of the triangle. Then you must create the ratio.

To do so, you need to find the two corresponding sides to compare. TTHat would be BC and EF. When you simplify the ratio, you dertermine what the scale factor is. In this case, it is 3, the correct answer to this question. The triangle DEF is 1/3 of its size.