Finding the Fourth Proportional to 1,387.38, 1,915.20 and 863.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.38 : 1,915.20 = 863.76 : x
2. Step 2: Convert to fraction form
   1,387.38/1,915.20 = 863.76/x
3. Step 3: Cross multiply
   1,387.38x = 1,915.20 × 863.76
4. Step 4: Simplify right side
   1,387.38x = 1,654,273.15
5. Step 5: Solve for x
   x = 1,654,273.15/1,387.38
6. Step 6: Final answer
   x = 1,192.37