Finding the Third Proportional to 640 and 1,329.50

Step by Step Solution

1. Step 1: Write the proportion equation
   640 : 1,329.50 = 1,329.50 : x
2. Step 2: Convert to fraction form
   640/1,329.50 = 1,329.50/x
3. Step 3: Cross multiply
   640x = 1,329.50 × 1,329.50
4. Step 4: Simplify right side
   640x = 1,767,570.25
5. Step 5: Solve for x
   x = 1,767,570.25/640
6. Step 6: Final answer
   x = 2,761.83