Finding the Third Proportional to 309.45 and 667.20

Step by Step Solution

1. Step 1: Write the proportion equation
   309.45 : 667.20 = 667.20 : x
2. Step 2: Convert to fraction form
   309.45/667.20 = 667.20/x
3. Step 3: Cross multiply
   309.45x = 667.20 × 667.20
4. Step 4: Simplify right side
   309.45x = 445,149.59
5. Step 5: Solve for x
   x = 445,149.59/309.45
6. Step 6: Final answer
   x = 1,438.54