Finding the Fourth Proportional to 2,620.35, 3,928.09 and 1,386.72

Step by Step Solution

1. Step 1: Write the proportion equation
   2,620.35 : 3,928.09 = 1,386.72 : x
2. Step 2: Convert to fraction form
   2,620.35/3,928.09 = 1,386.72/x
3. Step 3: Cross multiply
   2,620.35x = 3,928.09 × 1,386.72
4. Step 4: Simplify right side
   2,620.35x = 5,447,160.96
5. Step 5: Solve for x
   x = 5,447,160.96/2,620.35
6. Step 6: Final answer
   x = 2,078.79