Finding the Third Proportional to 391.31 and 840.56

Step by Step Solution

1. Step 1: Write the proportion equation
   391.31 : 840.56 = 840.56 : x
2. Step 2: Convert to fraction form
   391.31/840.56 = 840.56/x
3. Step 3: Cross multiply
   391.31x = 840.56 × 840.56
4. Step 4: Simplify right side
   391.31x = 706,545.32
5. Step 5: Solve for x
   x = 706,545.32/391.31
6. Step 6: Final answer
   x = 1,805.58