Finding the Fourth Proportional to 1,387.89, 1,915.29 and 766.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.89 : 1,915.29 = 766.89 : x
2. Step 2: Convert to fraction form
   1,387.89/1,915.29 = 766.89/x
3. Step 3: Cross multiply
   1,387.89x = 1,915.29 × 766.89
4. Step 4: Simplify right side
   1,387.89x = 1,468,816.75
5. Step 5: Solve for x
   x = 1,468,816.75/1,387.89
6. Step 6: Final answer
   x = 1,058.31