Finding the Third Proportional to 128.38 and 198.15

Step by Step Solution

1. Step 1: Write the proportion equation
   128.38 : 198.15 = 198.15 : x
2. Step 2: Convert to fraction form
   128.38/198.15 = 198.15/x
3. Step 3: Cross multiply
   128.38x = 198.15 × 198.15
4. Step 4: Simplify right side
   128.38x = 39,263.19
5. Step 5: Solve for x
   x = 39,263.19/128.38
6. Step 6: Final answer
   x = 305.83