Finding the Third Proportional to 261,686 and 402,789

Step by Step Solution

1. Step 1: Write the proportion equation
   261,686 : 402,789 = 402,789 : x
2. Step 2: Convert to fraction form
   261,686/402,789 = 402,789/x
3. Step 3: Cross multiply
   261,686x = 402,789 × 402,789
4. Step 4: Simplify right side
   261,686x = 162,238,978,521
5. Step 5: Solve for x
   x = 162,238,978,521/261,686
6. Step 6: Final answer
   x = 619,975.77