Finding the Fourth Proportional to 3,123.72, 4,685.64 and 815.28

Step by Step Solution

1. Step 1: Write the proportion equation
   3,123.72 : 4,685.64 = 815.28 : x
2. Step 2: Convert to fraction form
   3,123.72/4,685.64 = 815.28/x
3. Step 3: Cross multiply
   3,123.72x = 4,685.64 × 815.28
4. Step 4: Simplify right side
   3,123.72x = 3,820,108.58
5. Step 5: Solve for x
   x = 3,820,108.58/3,123.72
6. Step 6: Final answer
   x = 1,222.94