Finding the Fourth Proportional to 1,123.30, 1,685.71 and 392.88

Step by Step Solution

1. Step 1: Write the proportion equation
   1,123.30 : 1,685.71 = 392.88 : x
2. Step 2: Convert to fraction form
   1,123.30/1,685.71 = 392.88/x
3. Step 3: Cross multiply
   1,123.30x = 1,685.71 × 392.88
4. Step 4: Simplify right side
   1,123.30x = 662,288.56
5. Step 5: Solve for x
   x = 662,288.56/1,123.30
6. Step 6: Final answer
   x = 589.59