Finding the Fourth Proportional to 21,878.91, 30,192.89 and 12,929.63

Step by Step Solution

1. Step 1: Write the proportion equation
   21,878.91 : 30,192.89 = 12,929.63 : x
2. Step 2: Convert to fraction form
   21,878.91/30,192.89 = 12,929.63/x
3. Step 3: Cross multiply
   21,878.91x = 30,192.89 × 12,929.63
4. Step 4: Simplify right side
   21,878.91x = 390,382,680.72
5. Step 5: Solve for x
   x = 390,382,680.72/21,878.91
6. Step 6: Final answer
   x = 17,842.88