Finding the Third Proportional to 645 and 1,309.50

Step by Step Solution

1. Step 1: Write the proportion equation
   645 : 1,309.50 = 1,309.50 : x
2. Step 2: Convert to fraction form
   645/1,309.50 = 1,309.50/x
3. Step 3: Cross multiply
   645x = 1,309.50 × 1,309.50
4. Step 4: Simplify right side
   645x = 1,714,790.25
5. Step 5: Solve for x
   x = 1,714,790.25/645
6. Step 6: Final answer
   x = 2,658.59