Finding the Fourth Proportional to 9,999.17, 15,007.89 and 5,072.21

Step by Step Solution

1. Step 1: Write the proportion equation
   9,999.17 : 15,007.89 = 5,072.21 : x
2. Step 2: Convert to fraction form
   9,999.17/15,007.89 = 5,072.21/x
3. Step 3: Cross multiply
   9,999.17x = 15,007.89 × 5,072.21
4. Step 4: Simplify right side
   9,999.17x = 76,123,094.70
5. Step 5: Solve for x
   x = 76,123,094.70/9,999.17
6. Step 6: Final answer
   x = 7,612.95