Finding the Third Proportional to 142.38 and 309.45

Step by Step Solution

1. Step 1: Write the proportion equation
   142.38 : 309.45 = 309.45 : x
2. Step 2: Convert to fraction form
   142.38/309.45 = 309.45/x
3. Step 3: Cross multiply
   142.38x = 309.45 × 309.45
4. Step 4: Simplify right side
   142.38x = 95,756.40
5. Step 5: Solve for x
   x = 95,756.40/142.38
6. Step 6: Final answer
   x = 672.53