What you’ll learn
Solve missing-side problems.
Key idea
Image/original defines the forward scale factor; reversing the direction requires its inverse.
Use the stated vertex correspondence and image/original ratio; distinguish forward and inverse directions.
Worked example
Enter the exact value or ordered values in the format requested below.
Triangles ABC and DEF are similar in that order. AB=12, BC=16, AC=20, DE=6. Find EF.
- AB corresponds to DE, so image/original=6/12=1/2.
- BC corresponds to EF; EF=16*1/2=8.
Answer: 8
Quick Check
Evaluate a worked attempt at solve missing-side problems, identify the first invalid step, and provide the correction.
Triangles ABC and DEF are similar in that order: AB=3, BC=4, AC=5, DE=3/2. Student Step 1 gets forward factor 1/2. Step 2 divides BC by this factor and gives EF=8. Find the first invalid step and correct EF.