Finding the Third Proportional to 256,764.94 and 399,142.69

Step by Step Solution

1. Step 1: Write the proportion equation
   256,764.94 : 399,142.69 = 399,142.69 : x
2. Step 2: Convert to fraction form
   256,764.94/399,142.69 = 399,142.69/x
3. Step 3: Cross multiply
   256,764.94x = 399,142.69 × 399,142.69
4. Step 4: Simplify right side
   256,764.94x = 159,314,884,984.72
5. Step 5: Solve for x
   x = 159,314,884,984.72/256,764.94
6. Step 6: Final answer
   x = 620,469.78