Finding the Fourth Proportional to 1,388.43, 1,914.57 and 863.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.43 : 1,914.57 = 863.55 : x
2. Step 2: Convert to fraction form
   1,388.43/1,914.57 = 863.55/x
3. Step 3: Cross multiply
   1,388.43x = 1,914.57 × 863.55
4. Step 4: Simplify right side
   1,388.43x = 1,653,326.92
5. Step 5: Solve for x
   x = 1,653,326.92/1,388.43
6. Step 6: Final answer
   x = 1,190.79