Finding the Fourth Proportional to 1,152.50, 1,728.72 and 421.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,152.50 : 1,728.72 = 421.78 : x
2. Step 2: Convert to fraction form
   1,152.50/1,728.72 = 421.78/x
3. Step 3: Cross multiply
   1,152.50x = 1,728.72 × 421.78
4. Step 4: Simplify right side
   1,152.50x = 729,139.52
5. Step 5: Solve for x
   x = 729,139.52/1,152.50
6. Step 6: Final answer
   x = 632.66