Finding the Third Proportional to 811.69 and 1,685.39

Step by Step Solution

1. Step 1: Write the proportion equation
   811.69 : 1,685.39 = 1,685.39 : x
2. Step 2: Convert to fraction form
   811.69/1,685.39 = 1,685.39/x
3. Step 3: Cross multiply
   811.69x = 1,685.39 × 1,685.39
4. Step 4: Simplify right side
   811.69x = 2,840,541.56
5. Step 5: Solve for x
   x = 2,840,541.56/811.69
6. Step 6: Final answer
   x = 3,499.55