Finding the Third Proportional to 313.69 and 688.31

Step by Step Solution

1. Step 1: Write the proportion equation
   313.69 : 688.31 = 688.31 : x
2. Step 2: Convert to fraction form
   313.69/688.31 = 688.31/x
3. Step 3: Cross multiply
   313.69x = 688.31 × 688.31
4. Step 4: Simplify right side
   313.69x = 473,774.10
5. Step 5: Solve for x
   x = 473,774.10/313.69
6. Step 6: Final answer
   x = 1,510.34