Finding the Third Proportional to 390,359 and 582,290

Step by Step Solution

1. Step 1: Write the proportion equation
   390,359 : 582,290 = 582,290 : x
2. Step 2: Convert to fraction form
   390,359/582,290 = 582,290/x
3. Step 3: Cross multiply
   390,359x = 582,290 × 582,290
4. Step 4: Simplify right side
   390,359x = 339,061,644,100
5. Step 5: Solve for x
   x = 339,061,644,100/390,359
6. Step 6: Final answer
   x = 868,589.28