Finding the Fourth Proportional to 20,459.89, 28,235.81 and 13,642.15

Step by Step Solution

1. Step 1: Write the proportion equation
   20,459.89 : 28,235.81 = 13,642.15 : x
2. Step 2: Convert to fraction form
   20,459.89/28,235.81 = 13,642.15/x
3. Step 3: Cross multiply
   20,459.89x = 28,235.81 × 13,642.15
4. Step 4: Simplify right side
   20,459.89x = 385,197,155.39
5. Step 5: Solve for x
   x = 385,197,155.39/20,459.89
6. Step 6: Final answer
   x = 18,826.94