Finding the Fourth Proportional to 2,139.72, 3,209.04 and 840.48

Step by Step Solution

1. Step 1: Write the proportion equation
   2,139.72 : 3,209.04 = 840.48 : x
2. Step 2: Convert to fraction form
   2,139.72/3,209.04 = 840.48/x
3. Step 3: Cross multiply
   2,139.72x = 3,209.04 × 840.48
4. Step 4: Simplify right side
   2,139.72x = 2,697,133.94
5. Step 5: Solve for x
   x = 2,697,133.94/2,139.72
6. Step 6: Final answer
   x = 1,260.51