Finding the Fourth Proportional to 1,385.20, 1,911.60 and 825.99

Step by Step Solution

1. Step 1: Write the proportion equation
   1,385.20 : 1,911.60 = 825.99 : x
2. Step 2: Convert to fraction form
   1,385.20/1,911.60 = 825.99/x
3. Step 3: Cross multiply
   1,385.20x = 1,911.60 × 825.99
4. Step 4: Simplify right side
   1,385.20x = 1,578,963.13
5. Step 5: Solve for x
   x = 1,578,963.13/1,385.20
6. Step 6: Final answer
   x = 1,139.88