Finding the Fourth Proportional to 21,478.86, 29,638.34 and 12,986.10

Step by Step Solution

1. Step 1: Write the proportion equation
   21,478.86 : 29,638.34 = 12,986.10 : x
2. Step 2: Convert to fraction form
   21,478.86/29,638.34 = 12,986.10/x
3. Step 3: Cross multiply
   21,478.86x = 29,638.34 × 12,986.10
4. Step 4: Simplify right side
   21,478.86x = 384,886,447.07
5. Step 5: Solve for x
   x = 384,886,447.07/21,478.86
6. Step 6: Final answer
   x = 17,919.31