Finding the Fourth Proportional to 2,140.24, 3,208.76 and 840.72

Step by Step Solution

1. Step 1: Write the proportion equation
   2,140.24 : 3,208.76 = 840.72 : x
2. Step 2: Convert to fraction form
   2,140.24/3,208.76 = 840.72/x
3. Step 3: Cross multiply
   2,140.24x = 3,208.76 × 840.72
4. Step 4: Simplify right side
   2,140.24x = 2,697,668.71
5. Step 5: Solve for x
   x = 2,697,668.71/2,140.24
6. Step 6: Final answer
   x = 1,260.45