Finding the Fourth Proportional to 1,008.57, 1,391.90 and 615.81

Step by Step Solution

1. Step 1: Write the proportion equation
   1,008.57 : 1,391.90 = 615.81 : x
2. Step 2: Convert to fraction form
   1,008.57/1,391.90 = 615.81/x
3. Step 3: Cross multiply
   1,008.57x = 1,391.90 × 615.81
4. Step 4: Simplify right side
   1,008.57x = 857,142.86
5. Step 5: Solve for x
   x = 857,142.86/1,008.57
6. Step 6: Final answer
   x = 849.86