Finding the Third Proportional to 262,645 and 390,139

Step by Step Solution

1. Step 1: Write the proportion equation
   262,645 : 390,139 = 390,139 : x
2. Step 2: Convert to fraction form
   262,645/390,139 = 390,139/x
3. Step 3: Cross multiply
   262,645x = 390,139 × 390,139
4. Step 4: Simplify right side
   262,645x = 152,208,439,321
5. Step 5: Solve for x
   x = 152,208,439,321/262,645
6. Step 6: Final answer
   x = 579,521.56