Finding the Fourth Proportional to 1,200.72, 1,800.72 and 431.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,200.72 : 1,800.72 = 431.28 : x
2. Step 2: Convert to fraction form
   1,200.72/1,800.72 = 431.28/x
3. Step 3: Cross multiply
   1,200.72x = 1,800.72 × 431.28
4. Step 4: Simplify right side
   1,200.72x = 776,614.52
5. Step 5: Solve for x
   x = 776,614.52/1,200.72
6. Step 6: Final answer
   x = 646.79