Finding the Fourth Proportional to 1,388.25, 1,915.05 and 863.91

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.25 : 1,915.05 = 863.91 : x
2. Step 2: Convert to fraction form
   1,388.25/1,915.05 = 863.91/x
3. Step 3: Cross multiply
   1,388.25x = 1,915.05 × 863.91
4. Step 4: Simplify right side
   1,388.25x = 1,654,430.85
5. Step 5: Solve for x
   x = 1,654,430.85/1,388.25
6. Step 6: Final answer
   x = 1,191.74