Finding the Third Proportional to 978.75 and 2,158.31

Step by Step Solution

1. Step 1: Write the proportion equation
   978.75 : 2,158.31 = 2,158.31 : x
2. Step 2: Convert to fraction form
   978.75/2,158.31 = 2,158.31/x
3. Step 3: Cross multiply
   978.75x = 2,158.31 × 2,158.31
4. Step 4: Simplify right side
   978.75x = 4,658,312.85
5. Step 5: Solve for x
   x = 4,658,312.85/978.75
6. Step 6: Final answer
   x = 4,759.45