Finding the Fourth Proportional to 9,915.72, 13,683.90 and 5,439.21

Step by Step Solution

1. Step 1: Write the proportion equation
   9,915.72 : 13,683.90 = 5,439.21 : x
2. Step 2: Convert to fraction form
   9,915.72/13,683.90 = 5,439.21/x
3. Step 3: Cross multiply
   9,915.72x = 13,683.90 × 5,439.21
4. Step 4: Simplify right side
   9,915.72x = 74,429,605.72
5. Step 5: Solve for x
   x = 74,429,605.72/9,915.72
6. Step 6: Final answer
   x = 7,506.22