Finding the Fourth Proportional to 9,919.12, 13,687.40 and 5,728.72

Step by Step Solution

1. Step 1: Write the proportion equation
   9,919.12 : 13,687.40 = 5,728.72 : x
2. Step 2: Convert to fraction form
   9,919.12/13,687.40 = 5,728.72/x
3. Step 3: Cross multiply
   9,919.12x = 13,687.40 × 5,728.72
4. Step 4: Simplify right side
   9,919.12x = 78,411,282.13
5. Step 5: Solve for x
   x = 78,411,282.13/9,919.12
6. Step 6: Final answer
   x = 7,905.06