Finding the Fourth Proportional to 1,550.31, 2,139.33 and 920.90

Step by Step Solution

1. Step 1: Write the proportion equation
   1,550.31 : 2,139.33 = 920.90 : x
2. Step 2: Convert to fraction form
   1,550.31/2,139.33 = 920.90/x
3. Step 3: Cross multiply
   1,550.31x = 2,139.33 × 920.90
4. Step 4: Simplify right side
   1,550.31x = 1,970,098.30
5. Step 5: Solve for x
   x = 1,970,098.30/1,550.31
6. Step 6: Final answer
   x = 1,270.78