Finding the Third Proportional to 2,138.20 and 3,415.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,138.20 : 3,415.78 = 3,415.78 : x
2. Step 2: Convert to fraction form
   2,138.20/3,415.78 = 3,415.78/x
3. Step 3: Cross multiply
   2,138.20x = 3,415.78 × 3,415.78
4. Step 4: Simplify right side
   2,138.20x = 11,667,561.55
5. Step 5: Solve for x
   x = 11,667,561.55/2,138.20
6. Step 6: Final answer
   x = 5,456.71