Finding the Fourth Proportional to 1,978.57, 2,730.63 and 1,139.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,978.57 : 2,730.63 = 1,139.31 : x
2. Step 2: Convert to fraction form
   1,978.57/2,730.63 = 1,139.31/x
3. Step 3: Cross multiply
   1,978.57x = 2,730.63 × 1,139.31
4. Step 4: Simplify right side
   1,978.57x = 3,111,020.41
5. Step 5: Solve for x
   x = 3,111,020.41/1,978.57
6. Step 6: Final answer
   x = 1,572.36