Finding the Fourth Proportional to 1,142.20, 1,576.15 and 638.07

Step by Step Solution

1. Step 1: Write the proportion equation
   1,142.20 : 1,576.15 = 638.07 : x
2. Step 2: Convert to fraction form
   1,142.20/1,576.15 = 638.07/x
3. Step 3: Cross multiply
   1,142.20x = 1,576.15 × 638.07
4. Step 4: Simplify right side
   1,142.20x = 1,005,694.03
5. Step 5: Solve for x
   x = 1,005,694.03/1,142.20
6. Step 6: Final answer
   x = 880.49