Finding the Fourth Proportional to 1,380.88, 1,905.06 and 856.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.88 : 1,905.06 = 856.72 : x
2. Step 2: Convert to fraction form
   1,380.88/1,905.06 = 856.72/x
3. Step 3: Cross multiply
   1,380.88x = 1,905.06 × 856.72
4. Step 4: Simplify right side
   1,380.88x = 1,632,103.00
5. Step 5: Solve for x
   x = 1,632,103.00/1,380.88
6. Step 6: Final answer
   x = 1,181.93