Finding the Fourth Proportional to 12,640.31, 17,438.51 and 7,856.85

Step by Step Solution

1. Step 1: Write the proportion equation
   12,640.31 : 17,438.51 = 7,856.85 : x
2. Step 2: Convert to fraction form
   12,640.31/17,438.51 = 7,856.85/x
3. Step 3: Cross multiply
   12,640.31x = 17,438.51 × 7,856.85
4. Step 4: Simplify right side
   12,640.31x = 137,011,842.33
5. Step 5: Solve for x
   x = 137,011,842.33/12,640.31
6. Step 6: Final answer
   x = 10,839.28