Finding the Fourth Proportional to 1,405.72, 2,105.88 and 787.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,405.72 : 2,105.88 = 787.55 : x
2. Step 2: Convert to fraction form
   1,405.72/2,105.88 = 787.55/x
3. Step 3: Cross multiply
   1,405.72x = 2,105.88 × 787.55
4. Step 4: Simplify right side
   1,405.72x = 1,658,485.79
5. Step 5: Solve for x
   x = 1,658,485.79/1,405.72
6. Step 6: Final answer
   x = 1,179.81