Finding the Third Proportional to 391,978 and 858,688

Step by Step Solution

1. Step 1: Write the proportion equation
   391,978 : 858,688 = 858,688 : x
2. Step 2: Convert to fraction form
   391,978/858,688 = 858,688/x
3. Step 3: Cross multiply
   391,978x = 858,688 × 858,688
4. Step 4: Simplify right side
   391,978x = 737,345,081,344
5. Step 5: Solve for x
   x = 737,345,081,344/391,978
6. Step 6: Final answer
   x = 1,881,087.92