Finding the Third Proportional to 427.50 and 688.50

Step by Step Solution

1. Step 1: Write the proportion equation
   427.50 : 688.50 = 688.50 : x
2. Step 2: Convert to fraction form
   427.50/688.50 = 688.50/x
3. Step 3: Cross multiply
   427.50x = 688.50 × 688.50
4. Step 4: Simplify right side
   427.50x = 474,032.25
5. Step 5: Solve for x
   x = 474,032.25/427.50
6. Step 6: Final answer
   x = 1,108.85