Finding the Fourth Proportional to 5,139.90, 7,215.30 and 5,139.90

Step by Step Solution

1. Step 1: Write the proportion equation
   5,139.90 : 7,215.30 = 5,139.90 : x
2. Step 2: Convert to fraction form
   5,139.90/7,215.30 = 5,139.90/x
3. Step 3: Cross multiply
   5,139.90x = 7,215.30 × 5,139.90
4. Step 4: Simplify right side
   5,139.90x = 37,085,920.47
5. Step 5: Solve for x
   x = 37,085,920.47/5,139.90
6. Step 6: Final answer
   x = 7,215.30