Finding the Fourth Proportional to 21,471.08, 29,629.20 and 12,978.18

Step by Step Solution

1. Step 1: Write the proportion equation
   21,471.08 : 29,629.20 = 12,978.18 : x
2. Step 2: Convert to fraction form
   21,471.08/29,629.20 = 12,978.18/x
3. Step 3: Cross multiply
   21,471.08x = 29,629.20 × 12,978.18
4. Step 4: Simplify right side
   21,471.08x = 384,533,090.86
5. Step 5: Solve for x
   x = 384,533,090.86/21,471.08
6. Step 6: Final answer
   x = 17,909.35