Finding the Third Proportional to 300,828 and 643,128

Step by Step Solution

1. Step 1: Write the proportion equation
   300,828 : 643,128 = 643,128 : x
2. Step 2: Convert to fraction form
   300,828/643,128 = 643,128/x
3. Step 3: Cross multiply
   300,828x = 643,128 × 643,128
4. Step 4: Simplify right side
   300,828x = 413,613,624,384
5. Step 5: Solve for x
   x = 413,613,624,384/300,828
6. Step 6: Final answer
   x = 1,374,917.31