Finding the Fourth Proportional to 1,131.15, 1,560.96 and 665.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,131.15 : 1,560.96 = 665.40 : x
2. Step 2: Convert to fraction form
   1,131.15/1,560.96 = 665.40/x
3. Step 3: Cross multiply
   1,131.15x = 1,560.96 × 665.40
4. Step 4: Simplify right side
   1,131.15x = 1,038,662.78
5. Step 5: Solve for x
   x = 1,038,662.78/1,131.15
6. Step 6: Final answer
   x = 918.24