Finding the Third Proportional to 866.50 and 1,311.50

Step by Step Solution

1. Step 1: Write the proportion equation
   866.50 : 1,311.50 = 1,311.50 : x
2. Step 2: Convert to fraction form
   866.50/1,311.50 = 1,311.50/x
3. Step 3: Cross multiply
   866.50x = 1,311.50 × 1,311.50
4. Step 4: Simplify right side
   866.50x = 1,720,032.25
5. Step 5: Solve for x
   x = 1,720,032.25/866.50
6. Step 6: Final answer
   x = 1,985.03