Finding the Third Proportional to 128.69 and 251.38

Step by Step Solution

1. Step 1: Write the proportion equation
   128.69 : 251.38 = 251.38 : x
2. Step 2: Convert to fraction form
   128.69/251.38 = 251.38/x
3. Step 3: Cross multiply
   128.69x = 251.38 × 251.38
4. Step 4: Simplify right side
   128.69x = 63,189.39
5. Step 5: Solve for x
   x = 63,189.39/128.69
6. Step 6: Final answer
   x = 491.03