Finding the Third Proportional to 390.56 and 522.56

Step by Step Solution

1. Step 1: Write the proportion equation
   390.56 : 522.56 = 522.56 : x
2. Step 2: Convert to fraction form
   390.56/522.56 = 522.56/x
3. Step 3: Cross multiply
   390.56x = 522.56 × 522.56
4. Step 4: Simplify right side
   390.56x = 273,071.57
5. Step 5: Solve for x
   x = 273,071.57/390.56
6. Step 6: Final answer
   x = 699.18