Finding the Fourth Proportional to 10,978.80, 16,470.32 and 7,990.96

Step by Step Solution

1. Step 1: Write the proportion equation
   10,978.80 : 16,470.32 = 7,990.96 : x
2. Step 2: Convert to fraction form
   10,978.80/16,470.32 = 7,990.96/x
3. Step 3: Cross multiply
   10,978.80x = 16,470.32 × 7,990.96
4. Step 4: Simplify right side
   10,978.80x = 131,613,668.31
5. Step 5: Solve for x
   x = 131,613,668.31/10,978.80
6. Step 6: Final answer
   x = 11,987.98