Finding the Third Proportional to 209.25 and 316.50

Step by Step Solution

1. Step 1: Write the proportion equation
   209.25 : 316.50 = 316.50 : x
2. Step 2: Convert to fraction form
   209.25/316.50 = 316.50/x
3. Step 3: Cross multiply
   209.25x = 316.50 × 316.50
4. Step 4: Simplify right side
   209.25x = 100,172.25
5. Step 5: Solve for x
   x = 100,172.25/209.25
6. Step 6: Final answer
   x = 478.72