Finding the Third Proportional to 399.56 and 525.56

Step by Step Solution

1. Step 1: Write the proportion equation
   399.56 : 525.56 = 525.56 : x
2. Step 2: Convert to fraction form
   399.56/525.56 = 525.56/x
3. Step 3: Cross multiply
   399.56x = 525.56 × 525.56
4. Step 4: Simplify right side
   399.56x = 276,215.94
5. Step 5: Solve for x
   x = 276,215.94/399.56
6. Step 6: Final answer
   x = 691.30