Finding the Fourth Proportional to 1,139.34, 1,710.15 and 810.65

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.34 : 1,710.15 = 810.65 : x
2. Step 2: Convert to fraction form
   1,139.34/1,710.15 = 810.65/x
3. Step 3: Cross multiply
   1,139.34x = 1,710.15 × 810.65
4. Step 4: Simplify right side
   1,139.34x = 1,386,324.55
5. Step 5: Solve for x
   x = 1,386,324.55/1,139.34
6. Step 6: Final answer
   x = 1,216.78