Finding the Fourth Proportional to 20,856.96, 28,781.76 and 12,478.08

Step by Step Solution

1. Step 1: Write the proportion equation
   20,856.96 : 28,781.76 = 12,478.08 : x
2. Step 2: Convert to fraction form
   20,856.96/28,781.76 = 12,478.08/x
3. Step 3: Cross multiply
   20,856.96x = 28,781.76 × 12,478.08
4. Step 4: Simplify right side
   20,856.96x = 359,141,103.82
5. Step 5: Solve for x
   x = 359,141,103.82/20,856.96
6. Step 6: Final answer
   x = 17,219.24