Finding the Fourth Proportional to 1,386.10, 2,081.18 and 840.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.10 : 2,081.18 = 840.57 : x
2. Step 2: Convert to fraction form
   1,386.10/2,081.18 = 840.57/x
3. Step 3: Cross multiply
   1,386.10x = 2,081.18 × 840.57
4. Step 4: Simplify right side
   1,386.10x = 1,749,362.86
5. Step 5: Solve for x
   x = 1,749,362.86/1,386.10
6. Step 6: Final answer
   x = 1,262.08