Finding the Third Proportional to 128.50 and 209.25

Step by Step Solution

1. Step 1: Write the proportion equation
   128.50 : 209.25 = 209.25 : x
2. Step 2: Convert to fraction form
   128.50/209.25 = 209.25/x
3. Step 3: Cross multiply
   128.50x = 209.25 × 209.25
4. Step 4: Simplify right side
   128.50x = 43,785.56
5. Step 5: Solve for x
   x = 43,785.56/128.50
6. Step 6: Final answer
   x = 340.74