Finding the Fourth Proportional to 1,391.42, 2,085.72 and 775.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.42 : 2,085.72 = 775.40 : x
2. Step 2: Convert to fraction form
   1,391.42/2,085.72 = 775.40/x
3. Step 3: Cross multiply
   1,391.42x = 2,085.72 × 775.40
4. Step 4: Simplify right side
   1,391.42x = 1,617,267.29
5. Step 5: Solve for x
   x = 1,617,267.29/1,391.42
6. Step 6: Final answer
   x = 1,162.31