Finding the Fourth Proportional to 978.89, 1,351.35 and 685.71

Step by Step Solution

1. Step 1: Write the proportion equation
   978.89 : 1,351.35 = 685.71 : x
2. Step 2: Convert to fraction form
   978.89/1,351.35 = 685.71/x
3. Step 3: Cross multiply
   978.89x = 1,351.35 × 685.71
4. Step 4: Simplify right side
   978.89x = 926,634.21
5. Step 5: Solve for x
   x = 926,634.21/978.89
6. Step 6: Final answer
   x = 946.62