Finding the Fourth Proportional to 1,006.86, 1,385.59 and 978.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,006.86 : 1,385.59 = 978.31 : x
2. Step 2: Convert to fraction form
   1,006.86/1,385.59 = 978.31/x
3. Step 3: Cross multiply
   1,006.86x = 1,385.59 × 978.31
4. Step 4: Simplify right side
   1,006.86x = 1,355,524.73
5. Step 5: Solve for x
   x = 1,355,524.73/1,006.86
6. Step 6: Final answer
   x = 1,346.29