Finding the Fourth Proportional to 13,136.78, 18,128.61 and 7,168.50

Step by Step Solution

1. Step 1: Write the proportion equation
   13,136.78 : 18,128.61 = 7,168.50 : x
2. Step 2: Convert to fraction form
   13,136.78/18,128.61 = 7,168.50/x
3. Step 3: Cross multiply
   13,136.78x = 18,128.61 × 7,168.50
4. Step 4: Simplify right side
   13,136.78x = 129,954,940.79
5. Step 5: Solve for x
   x = 129,954,940.79/13,136.78
6. Step 6: Final answer
   x = 9,892.45