Finding the Third Proportional to 978.75 and 1,089

Step by Step Solution

1. Step 1: Write the proportion equation
   978.75 : 1,089 = 1,089 : x
2. Step 2: Convert to fraction form
   978.75/1,089 = 1,089/x
3. Step 3: Cross multiply
   978.75x = 1,089 × 1,089
4. Step 4: Simplify right side
   978.75x = 1,185,921
5. Step 5: Solve for x
   x = 1,185,921/978.75
6. Step 6: Final answer
   x = 1,211.67