Finding the Fourth Proportional to 13,459.72, 20,185.34 and 5,139.40

Step by Step Solution

1. Step 1: Write the proportion equation
   13,459.72 : 20,185.34 = 5,139.40 : x
2. Step 2: Convert to fraction form
   13,459.72/20,185.34 = 5,139.40/x
3. Step 3: Cross multiply
   13,459.72x = 20,185.34 × 5,139.40
4. Step 4: Simplify right side
   13,459.72x = 103,740,536.40
5. Step 5: Solve for x
   x = 103,740,536.40/13,459.72
6. Step 6: Final answer
   x = 7,707.48