Finding the Fourth Proportional to 21,172.74, 31,747.74 and 7,128.10

Step by Step Solution

1. Step 1: Write the proportion equation
   21,172.74 : 31,747.74 = 7,128.10 : x
2. Step 2: Convert to fraction form
   21,172.74/31,747.74 = 7,128.10/x
3. Step 3: Cross multiply
   21,172.74x = 31,747.74 × 7,128.10
4. Step 4: Simplify right side
   21,172.74x = 226,301,065.49
5. Step 5: Solve for x
   x = 226,301,065.49/21,172.74
6. Step 6: Final answer
   x = 10,688.32