Finding the Fourth Proportional to 2,156.47, 3,235.89 and 840.28

Step by Step Solution

1. Step 1: Write the proportion equation
   2,156.47 : 3,235.89 = 840.28 : x
2. Step 2: Convert to fraction form
   2,156.47/3,235.89 = 840.28/x
3. Step 3: Cross multiply
   2,156.47x = 3,235.89 × 840.28
4. Step 4: Simplify right side
   2,156.47x = 2,719,053.65
5. Step 5: Solve for x
   x = 2,719,053.65/2,156.47
6. Step 6: Final answer
   x = 1,260.88