Finding the Fourth Proportional to 13,985.31, 20,978.01 and 5,220.09

Step by Step Solution

1. Step 1: Write the proportion equation
   13,985.31 : 20,978.01 = 5,220.09 : x
2. Step 2: Convert to fraction form
   13,985.31/20,978.01 = 5,220.09/x
3. Step 3: Cross multiply
   13,985.31x = 20,978.01 × 5,220.09
4. Step 4: Simplify right side
   13,985.31x = 109,507,100.22
5. Step 5: Solve for x
   x = 109,507,100.22/13,985.31
6. Step 6: Final answer
   x = 7,830.15