Finding the Fourth Proportional to 1,139.75, 1,572.86 and 615.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.75 : 1,572.86 = 615.78 : x
2. Step 2: Convert to fraction form
   1,139.75/1,572.86 = 615.78/x
3. Step 3: Cross multiply
   1,139.75x = 1,572.86 × 615.78
4. Step 4: Simplify right side
   1,139.75x = 968,535.39
5. Step 5: Solve for x
   x = 968,535.39/1,139.75
6. Step 6: Final answer
   x = 849.78