Finding the Third Proportional to 143.72 and 309.80

Step by Step Solution

1. Step 1: Write the proportion equation
   143.72 : 309.80 = 309.80 : x
2. Step 2: Convert to fraction form
   143.72/309.80 = 309.80/x
3. Step 3: Cross multiply
   143.72x = 309.80 × 309.80
4. Step 4: Simplify right side
   143.72x = 95,974.10
5. Step 5: Solve for x
   x = 95,974.10/143.72
6. Step 6: Final answer
   x = 667.79