Finding the Fourth Proportional to 6,389.16, 8,815.68 and 3,870.78

Step by Step Solution

1. Step 1: Write the proportion equation
   6,389.16 : 8,815.68 = 3,870.78 : x
2. Step 2: Convert to fraction form
   6,389.16/8,815.68 = 3,870.78/x
3. Step 3: Cross multiply
   6,389.16x = 8,815.68 × 3,870.78
4. Step 4: Simplify right side
   6,389.16x = 34,123,557.83
5. Step 5: Solve for x
   x = 34,123,557.83/6,389.16
6. Step 6: Final answer
   x = 5,340.85