Finding the Fourth Proportional to 13,388.40, 18,475.74 and 7,420.05

Step by Step Solution

1. Step 1: Write the proportion equation
   13,388.40 : 18,475.74 = 7,420.05 : x
2. Step 2: Convert to fraction form
   13,388.40/18,475.74 = 7,420.05/x
3. Step 3: Cross multiply
   13,388.40x = 18,475.74 × 7,420.05
4. Step 4: Simplify right side
   13,388.40x = 137,090,914.59
5. Step 5: Solve for x
   x = 137,090,914.59/13,388.40
6. Step 6: Final answer
   x = 10,239.53