Finding the Fourth Proportional to 12,428.42, 17,128.40 and 11,639.27

Step by Step Solution

1. Step 1: Write the proportion equation
   12,428.42 : 17,128.40 = 11,639.27 : x
2. Step 2: Convert to fraction form
   12,428.42/17,128.40 = 11,639.27/x
3. Step 3: Cross multiply
   12,428.42x = 17,128.40 × 11,639.27
4. Step 4: Simplify right side
   12,428.42x = 199,362,056.89
5. Step 5: Solve for x
   x = 199,362,056.89/12,428.42
6. Step 6: Final answer
   x = 16,040.83