Finding the Third Proportional to 139.50 and 287

Step by Step Solution

1. Step 1: Write the proportion equation
   139.50 : 287 = 287 : x
2. Step 2: Convert to fraction form
   139.50/287 = 287/x
3. Step 3: Cross multiply
   139.50x = 287 × 287
4. Step 4: Simplify right side
   139.50x = 82,369
5. Step 5: Solve for x
   x = 82,369/139.50
6. Step 6: Final answer
   x = 590.46