Finding the Third Proportional to 129.50 and 287.50

Step by Step Solution

1. Step 1: Write the proportion equation
   129.50 : 287.50 = 287.50 : x
2. Step 2: Convert to fraction form
   129.50/287.50 = 287.50/x
3. Step 3: Cross multiply
   129.50x = 287.50 × 287.50
4. Step 4: Simplify right side
   129.50x = 82,656.25
5. Step 5: Solve for x
   x = 82,656.25/129.50
6. Step 6: Final answer
   x = 638.27