Finding the Third Proportional to 387.50 and 431.50

Step by Step Solution

1. Step 1: Write the proportion equation
   387.50 : 431.50 = 431.50 : x
2. Step 2: Convert to fraction form
   387.50/431.50 = 431.50/x
3. Step 3: Cross multiply
   387.50x = 431.50 × 431.50
4. Step 4: Simplify right side
   387.50x = 186,192.25
5. Step 5: Solve for x
   x = 186,192.25/387.50
6. Step 6: Final answer
   x = 480.50