Finding the Fourth Proportional to 2,559.60, 3,840.78 and 1,390.50

Step by Step Solution

1. Step 1: Write the proportion equation
   2,559.60 : 3,840.78 = 1,390.50 : x
2. Step 2: Convert to fraction form
   2,559.60/3,840.78 = 1,390.50/x
3. Step 3: Cross multiply
   2,559.60x = 3,840.78 × 1,390.50
4. Step 4: Simplify right side
   2,559.60x = 5,340,604.59
5. Step 5: Solve for x
   x = 5,340,604.59/2,559.60
6. Step 6: Final answer
   x = 2,086.50