Finding the Fourth Proportional to 1,128.85, 1,557.72 and 631.42

Step by Step Solution

1. Step 1: Write the proportion equation
   1,128.85 : 1,557.72 = 631.42 : x
2. Step 2: Convert to fraction form
   1,128.85/1,557.72 = 631.42/x
3. Step 3: Cross multiply
   1,128.85x = 1,557.72 × 631.42
4. Step 4: Simplify right side
   1,128.85x = 983,579.16
5. Step 5: Solve for x
   x = 983,579.16/1,128.85
6. Step 6: Final answer
   x = 871.31