Finding the Fourth Proportional to 9,866.78, 13,615.99 and 5,390.42

Step by Step Solution

1. Step 1: Write the proportion equation
   9,866.78 : 13,615.99 = 5,390.42 : x
2. Step 2: Convert to fraction form
   9,866.78/13,615.99 = 5,390.42/x
3. Step 3: Cross multiply
   9,866.78x = 13,615.99 × 5,390.42
4. Step 4: Simplify right side
   9,866.78x = 73,395,809.78
5. Step 5: Solve for x
   x = 73,395,809.78/9,866.78
6. Step 6: Final answer
   x = 7,438.68