Finding the Third Proportional to 839.81 and 1,288.69

Step by Step Solution

1. Step 1: Write the proportion equation
   839.81 : 1,288.69 = 1,288.69 : x
2. Step 2: Convert to fraction form
   839.81/1,288.69 = 1,288.69/x
3. Step 3: Cross multiply
   839.81x = 1,288.69 × 1,288.69
4. Step 4: Simplify right side
   839.81x = 1,660,715.47
5. Step 5: Solve for x
   x = 1,660,715.47/839.81
6. Step 6: Final answer
   x = 1,977.48