Finding the Third Proportional to 428.50 and 517.50

Step by Step Solution

1. Step 1: Write the proportion equation
   428.50 : 517.50 = 517.50 : x
2. Step 2: Convert to fraction form
   428.50/517.50 = 517.50/x
3. Step 3: Cross multiply
   428.50x = 517.50 × 517.50
4. Step 4: Simplify right side
   428.50x = 267,806.25
5. Step 5: Solve for x
   x = 267,806.25/428.50
6. Step 6: Final answer
   x = 624.99