Finding the Third Proportional to 420,417 and 642,978

Step by Step Solution

1. Step 1: Write the proportion equation
   420,417 : 642,978 = 642,978 : x
2. Step 2: Convert to fraction form
   420,417/642,978 = 642,978/x
3. Step 3: Cross multiply
   420,417x = 642,978 × 642,978
4. Step 4: Simplify right side
   420,417x = 413,420,708,484
5. Step 5: Solve for x
   x = 413,420,708,484/420,417
6. Step 6: Final answer
   x = 983,358.69