Finding the Fourth Proportional to 20,621.78, 30,911.00 and 13,131.09

Step by Step Solution

1. Step 1: Write the proportion equation
   20,621.78 : 30,911.00 = 13,131.09 : x
2. Step 2: Convert to fraction form
   20,621.78/30,911.00 = 13,131.09/x
3. Step 3: Cross multiply
   20,621.78x = 30,911.00 × 13,131.09
4. Step 4: Simplify right side
   20,621.78x = 405,895,057.33
5. Step 5: Solve for x
   x = 405,895,057.33/20,621.78
6. Step 6: Final answer
   x = 19,682.84