Finding the Fourth Proportional to 11,898.72, 16,422.96 and 7,920

Step by Step Solution

1. Step 1: Write the proportion equation
   11,898.72 : 16,422.96 = 7,920 : x
2. Step 2: Convert to fraction form
   11,898.72/16,422.96 = 7,920/x
3. Step 3: Cross multiply
   11,898.72x = 16,422.96 × 7,920
4. Step 4: Simplify right side
   11,898.72x = 130,069,843.20
5. Step 5: Solve for x
   x = 130,069,843.20/11,898.72
6. Step 6: Final answer
   x = 10,931.41