Finding the Third Proportional to 2,128.78 and 4,429.55

Step by Step Solution

1. Step 1: Write the proportion equation
   2,128.78 : 4,429.55 = 4,429.55 : x
2. Step 2: Convert to fraction form
   2,128.78/4,429.55 = 4,429.55/x
3. Step 3: Cross multiply
   2,128.78x = 4,429.55 × 4,429.55
4. Step 4: Simplify right side
   2,128.78x = 19,620,885.52
5. Step 5: Solve for x
   x = 19,620,885.52/2,128.78
6. Step 6: Final answer
   x = 9,216.96