Finding the Third Proportional to 511.31 and 685.34

Step by Step Solution

1. Step 1: Write the proportion equation
   511.31 : 685.34 = 685.34 : x
2. Step 2: Convert to fraction form
   511.31/685.34 = 685.34/x
3. Step 3: Cross multiply
   511.31x = 685.34 × 685.34
4. Step 4: Simplify right side
   511.31x = 469,685.35
5. Step 5: Solve for x
   x = 469,685.35/511.31
6. Step 6: Final answer
   x = 918.59