Finding the Third Proportional to 120,109.50 and 278,021.25

Step by Step Solution

1. Step 1: Write the proportion equation
   120,109.50 : 278,021.25 = 278,021.25 : x
2. Step 2: Convert to fraction form
   120,109.50/278,021.25 = 278,021.25/x
3. Step 3: Cross multiply
   120,109.50x = 278,021.25 × 278,021.25
4. Step 4: Simplify right side
   120,109.50x = 77,295,815,451.56
5. Step 5: Solve for x
   x = 77,295,815,451.56/120,109.50
6. Step 6: Final answer
   x = 643,544.56