Finding the Fourth Proportional to 9,991.86, 13,788.60 and 5,515.61

Step by Step Solution

1. Step 1: Write the proportion equation
   9,991.86 : 13,788.60 = 5,515.61 : x
2. Step 2: Convert to fraction form
   9,991.86/13,788.60 = 5,515.61/x
3. Step 3: Cross multiply
   9,991.86x = 13,788.60 × 5,515.61
4. Step 4: Simplify right side
   9,991.86x = 76,052,471.10
5. Step 5: Solve for x
   x = 76,052,471.10/9,991.86
6. Step 6: Final answer
   x = 7,611.44