Finding the Fourth Proportional to 3,123.89, 4,685.80 and 815.39

Step by Step Solution

1. Step 1: Write the proportion equation
   3,123.89 : 4,685.80 = 815.39 : x
2. Step 2: Convert to fraction form
   3,123.89/4,685.80 = 815.39/x
3. Step 3: Cross multiply
   3,123.89x = 4,685.80 × 815.39
4. Step 4: Simplify right side
   3,123.89x = 3,820,754.46
5. Step 5: Solve for x
   x = 3,820,754.46/3,123.89
6. Step 6: Final answer
   x = 1,223.08