Finding the Fourth Proportional to 1,389.76, 1,921.52 and 1,328.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.76 : 1,921.52 = 1,328.56 : x
2. Step 2: Convert to fraction form
   1,389.76/1,921.52 = 1,328.56/x
3. Step 3: Cross multiply
   1,389.76x = 1,921.52 × 1,328.56
4. Step 4: Simplify right side
   1,389.76x = 2,552,854.61
5. Step 5: Solve for x
   x = 2,552,854.61/1,389.76
6. Step 6: Final answer
   x = 1,836.90