Finding the Third Proportional to 300,428 and 643,504

Step by Step Solution

1. Step 1: Write the proportion equation
   300,428 : 643,504 = 643,504 : x
2. Step 2: Convert to fraction form
   300,428/643,504 = 643,504/x
3. Step 3: Cross multiply
   300,428x = 643,504 × 643,504
4. Step 4: Simplify right side
   300,428x = 414,097,398,016
5. Step 5: Solve for x
   x = 414,097,398,016/300,428
6. Step 6: Final answer
   x = 1,378,358.20