Finding the Fourth Proportional to 21,943.72, 30,282.78 and 12,991.06

Step by Step Solution

1. Step 1: Write the proportion equation
   21,943.72 : 30,282.78 = 12,991.06 : x
2. Step 2: Convert to fraction form
   21,943.72/30,282.78 = 12,991.06/x
3. Step 3: Cross multiply
   21,943.72x = 30,282.78 × 12,991.06
4. Step 4: Simplify right side
   21,943.72x = 393,405,411.95
5. Step 5: Solve for x
   x = 393,405,411.95/21,943.72
6. Step 6: Final answer
   x = 17,927.93