Finding the Third Proportional to 287.38 and 620.31

Step by Step Solution

1. Step 1: Write the proportion equation
   287.38 : 620.31 = 620.31 : x
2. Step 2: Convert to fraction form
   287.38/620.31 = 620.31/x
3. Step 3: Cross multiply
   287.38x = 620.31 × 620.31
4. Step 4: Simplify right side
   287.38x = 384,787.60
5. Step 5: Solve for x
   x = 384,787.60/287.38
6. Step 6: Final answer
   x = 1,338.97