Finding the Fourth Proportional to 1,388.52, 2,081.74 and 840.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.52 : 2,081.74 = 840.57 : x
2. Step 2: Convert to fraction form
   1,388.52/2,081.74 = 840.57/x
3. Step 3: Cross multiply
   1,388.52x = 2,081.74 × 840.57
4. Step 4: Simplify right side
   1,388.52x = 1,749,833.58
5. Step 5: Solve for x
   x = 1,749,833.58/1,388.52
6. Step 6: Final answer
   x = 1,260.22