Finding the Fourth Proportional to 1,391.60, 1,920.55 and 824.77

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.60 : 1,920.55 = 824.77 : x
2. Step 2: Convert to fraction form
   1,391.60/1,920.55 = 824.77/x
3. Step 3: Cross multiply
   1,391.60x = 1,920.55 × 824.77
4. Step 4: Simplify right side
   1,391.60x = 1,584,015.46
5. Step 5: Solve for x
   x = 1,584,015.46/1,391.60
6. Step 6: Final answer
   x = 1,138.27