Finding the Third Proportional to 118.50 and 217.50

Step by Step Solution

1. Step 1: Write the proportion equation
   118.50 : 217.50 = 217.50 : x
2. Step 2: Convert to fraction form
   118.50/217.50 = 217.50/x
3. Step 3: Cross multiply
   118.50x = 217.50 × 217.50
4. Step 4: Simplify right side
   118.50x = 47,306.25
5. Step 5: Solve for x
   x = 47,306.25/118.50
6. Step 6: Final answer
   x = 399.21