Finding the Third Proportional to 312,904 and 640,384

Step by Step Solution

1. Step 1: Write the proportion equation
   312,904 : 640,384 = 640,384 : x
2. Step 2: Convert to fraction form
   312,904/640,384 = 640,384/x
3. Step 3: Cross multiply
   312,904x = 640,384 × 640,384
4. Step 4: Simplify right side
   312,904x = 410,091,667,456
5. Step 5: Solve for x
   x = 410,091,667,456/312,904
6. Step 6: Final answer
   x = 1,310,598.99