Finding the Fourth Proportional to 9,405.21, 12,978.69 and 5,426.09

Step by Step Solution

1. Step 1: Write the proportion equation
   9,405.21 : 12,978.69 = 5,426.09 : x
2. Step 2: Convert to fraction form
   9,405.21/12,978.69 = 5,426.09/x
3. Step 3: Cross multiply
   9,405.21x = 12,978.69 × 5,426.09
4. Step 4: Simplify right side
   9,405.21x = 70,423,475.13
5. Step 5: Solve for x
   x = 70,423,475.13/9,405.21
6. Step 6: Final answer
   x = 7,487.71