Finding the Fourth Proportional to 21,980.72, 30,332.32 and 12,420.79

Step by Step Solution

1. Step 1: Write the proportion equation
   21,980.72 : 30,332.32 = 12,420.79 : x
2. Step 2: Convert to fraction form
   21,980.72/30,332.32 = 12,420.79/x
3. Step 3: Cross multiply
   21,980.72x = 30,332.32 × 12,420.79
4. Step 4: Simplify right side
   21,980.72x = 376,751,510.54
5. Step 5: Solve for x
   x = 376,751,510.54/21,980.72
6. Step 6: Final answer
   x = 17,140.09