Finding the Fourth Proportional to 1,080.86, 1,491.56 and 638.77

Step by Step Solution

1. Step 1: Write the proportion equation
   1,080.86 : 1,491.56 = 638.77 : x
2. Step 2: Convert to fraction form
   1,080.86/1,491.56 = 638.77/x
3. Step 3: Cross multiply
   1,080.86x = 1,491.56 × 638.77
4. Step 4: Simplify right side
   1,080.86x = 952,763.78
5. Step 5: Solve for x
   x = 952,763.78/1,080.86
6. Step 6: Final answer
   x = 881.49