Finding the Third Proportional to 643.69 and 1,405.38

Step by Step Solution

1. Step 1: Write the proportion equation
   643.69 : 1,405.38 = 1,405.38 : x
2. Step 2: Convert to fraction form
   643.69/1,405.38 = 1,405.38/x
3. Step 3: Cross multiply
   643.69x = 1,405.38 × 1,405.38
4. Step 4: Simplify right side
   643.69x = 1,975,078.89
5. Step 5: Solve for x
   x = 1,975,078.89/643.69
6. Step 6: Final answer
   x = 3,068.38