Finding the Fourth Proportional to 1,080.81, 1,491.71 and 638.73

Step by Step Solution

1. Step 1: Write the proportion equation
   1,080.81 : 1,491.71 = 638.73 : x
2. Step 2: Convert to fraction form
   1,080.81/1,491.71 = 638.73/x
3. Step 3: Cross multiply
   1,080.81x = 1,491.71 × 638.73
4. Step 4: Simplify right side
   1,080.81x = 952,796.73
5. Step 5: Solve for x
   x = 952,796.73/1,080.81
6. Step 6: Final answer
   x = 881.56