Finding the Fourth Proportional to 1,080.18, 1,490.90 and 687.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,080.18 : 1,490.90 = 687.15 : x
2. Step 2: Convert to fraction form
   1,080.18/1,490.90 = 687.15/x
3. Step 3: Cross multiply
   1,080.18x = 1,490.90 × 687.15
4. Step 4: Simplify right side
   1,080.18x = 1,024,468.50
5. Step 5: Solve for x
   x = 1,024,468.50/1,080.18
6. Step 6: Final answer
   x = 948.42