Finding the Fourth Proportional to 1,080.89, 1,491.72 and 638.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,080.89 : 1,491.72 = 638.79 : x
2. Step 2: Convert to fraction form
   1,080.89/1,491.72 = 638.79/x
3. Step 3: Cross multiply
   1,080.89x = 1,491.72 × 638.79
4. Step 4: Simplify right side
   1,080.89x = 952,887.83
5. Step 5: Solve for x
   x = 952,887.83/1,080.89
6. Step 6: Final answer
   x = 881.57