Finding the Third Proportional to 805 and 1,290.50

Step by Step Solution

1. Step 1: Write the proportion equation
   805 : 1,290.50 = 1,290.50 : x
2. Step 2: Convert to fraction form
   805/1,290.50 = 1,290.50/x
3. Step 3: Cross multiply
   805x = 1,290.50 × 1,290.50
4. Step 4: Simplify right side
   805x = 1,665,390.25
5. Step 5: Solve for x
   x = 1,665,390.25/805
6. Step 6: Final answer
   x = 2,068.81