Medea found the missing measure using a proportion of the reduced trapezoid.
A larger trapezoid has a top side length of 8 centimeters and left side length of 4 centimeters. A smaller trapezoid has a top side length of x centimeters and left side length of one-half centimeters.
1. Proportion: StartFraction 4 over x EndFraction = StartFraction 8 over one-half EndFraction. 2. Cross-products: 4 (one-half) = 8 (x). 3. Simplify: 2 = 8 x. 4. Divide: One-fourth = x.
Analyze Medea’s work. In which step did Medea make an error?
In step 1, the corresponding parts are in different positions.
In step 2, the cross products should be multiplied instead of being equal.
In step 3, she should have added instead of multiplying to simplify.
In step 4, she needed to divide 2 to both sides to get x = 4.