Finding the Third Proportional to 139.92 and 315.42

Step by Step Solution

1. Step 1: Write the proportion equation
   139.92 : 315.42 = 315.42 : x
2. Step 2: Convert to fraction form
   139.92/315.42 = 315.42/x
3. Step 3: Cross multiply
   139.92x = 315.42 × 315.42
4. Step 4: Simplify right side
   139.92x = 99,490.96
5. Step 5: Solve for x
   x = 99,490.96/139.92
6. Step 6: Final answer
   x = 711.05