Finding the Third Proportional to 643.50 and 1,399.50

Step by Step Solution

1. Step 1: Write the proportion equation
   643.50 : 1,399.50 = 1,399.50 : x
2. Step 2: Convert to fraction form
   643.50/1,399.50 = 1,399.50/x
3. Step 3: Cross multiply
   643.50x = 1,399.50 × 1,399.50
4. Step 4: Simplify right side
   643.50x = 1,958,600.25
5. Step 5: Solve for x
   x = 1,958,600.25/643.50
6. Step 6: Final answer
   x = 3,043.67