Finding the Third Proportional to 258.38 and 387.56

Step by Step Solution

1. Step 1: Write the proportion equation
   258.38 : 387.56 = 387.56 : x
2. Step 2: Convert to fraction form
   258.38/387.56 = 387.56/x
3. Step 3: Cross multiply
   258.38x = 387.56 × 387.56
4. Step 4: Simplify right side
   258.38x = 150,204.69
5. Step 5: Solve for x
   x = 150,204.69/258.38
6. Step 6: Final answer
   x = 581.34