Finding the Fourth Proportional to 21,109.76, 29,131.92 and 11,678.72

Step by Step Solution

1. Step 1: Write the proportion equation
   21,109.76 : 29,131.92 = 11,678.72 : x
2. Step 2: Convert to fraction form
   21,109.76/29,131.92 = 11,678.72/x
3. Step 3: Cross multiply
   21,109.76x = 29,131.92 × 11,678.72
4. Step 4: Simplify right side
   21,109.76x = 340,223,536.74
5. Step 5: Solve for x
   x = 340,223,536.74/21,109.76
6. Step 6: Final answer
   x = 16,116.88