Finding the Third Proportional to 639.50 and 1,400

Step by Step Solution

1. Step 1: Write the proportion equation
   639.50 : 1,400 = 1,400 : x
2. Step 2: Convert to fraction form
   639.50/1,400 = 1,400/x
3. Step 3: Cross multiply
   639.50x = 1,400 × 1,400
4. Step 4: Simplify right side
   639.50x = 1,960,000
5. Step 5: Solve for x
   x = 1,960,000/639.50
6. Step 6: Final answer
   x = 3,064.89