Finding the Third Proportional to 253.50 and 418.50

Step by Step Solution

1. Step 1: Write the proportion equation
   253.50 : 418.50 = 418.50 : x
2. Step 2: Convert to fraction form
   253.50/418.50 = 418.50/x
3. Step 3: Cross multiply
   253.50x = 418.50 × 418.50
4. Step 4: Simplify right side
   253.50x = 175,142.25
5. Step 5: Solve for x
   x = 175,142.25/253.50
6. Step 6: Final answer
   x = 690.90