Finding the Third Proportional to 861.89 and 1,218.59

Step by Step Solution

1. Step 1: Write the proportion equation
   861.89 : 1,218.59 = 1,218.59 : x
2. Step 2: Convert to fraction form
   861.89/1,218.59 = 1,218.59/x
3. Step 3: Cross multiply
   861.89x = 1,218.59 × 1,218.59
4. Step 4: Simplify right side
   861.89x = 1,484,951.69
5. Step 5: Solve for x
   x = 1,484,951.69/861.89
6. Step 6: Final answer
   x = 1,722.90