Finding the Fourth Proportional to 9,991.59, 13,788.40 and 5,515.35

Step by Step Solution

1. Step 1: Write the proportion equation
   9,991.59 : 13,788.40 = 5,515.35 : x
2. Step 2: Convert to fraction form
   9,991.59/13,788.40 = 5,515.35/x
3. Step 3: Cross multiply
   9,991.59x = 13,788.40 × 5,515.35
4. Step 4: Simplify right side
   9,991.59x = 76,047,796.79
5. Step 5: Solve for x
   x = 76,047,796.79/9,991.59
6. Step 6: Final answer
   x = 7,611.18