Finding the Third Proportional to 685,911 and 978,421

Step by Step Solution

1. Step 1: Write the proportion equation
   685,911 : 978,421 = 978,421 : x
2. Step 2: Convert to fraction form
   685,911/978,421 = 978,421/x
3. Step 3: Cross multiply
   685,911x = 978,421 × 978,421
4. Step 4: Simplify right side
   685,911x = 957,307,653,241
5. Step 5: Solve for x
   x = 957,307,653,241/685,911
6. Step 6: Final answer
   x = 1,395,673.28