Finding the Fourth Proportional to 21,158.72, 31,739.67 and 7,118.78

Step by Step Solution

1. Step 1: Write the proportion equation
   21,158.72 : 31,739.67 = 7,118.78 : x
2. Step 2: Convert to fraction form
   21,158.72/31,739.67 = 7,118.78/x
3. Step 3: Cross multiply
   21,158.72x = 31,739.67 × 7,118.78
4. Step 4: Simplify right side
   21,158.72x = 225,947,728.00
5. Step 5: Solve for x
   x = 225,947,728.00/21,158.72
6. Step 6: Final answer
   x = 10,678.70