Finding the Third Proportional to 977.91 and 2,128.78

Step by Step Solution

1. Step 1: Write the proportion equation
   977.91 : 2,128.78 = 2,128.78 : x
2. Step 2: Convert to fraction form
   977.91/2,128.78 = 2,128.78/x
3. Step 3: Cross multiply
   977.91x = 2,128.78 × 2,128.78
4. Step 4: Simplify right side
   977.91x = 4,531,709.61
5. Step 5: Solve for x
   x = 4,531,709.61/977.91
6. Step 6: Final answer
   x = 4,634.09