Finding the Fourth Proportional to 9,809.80, 13,538.10 and 5,561.20

Step by Step Solution

1. Step 1: Write the proportion equation
   9,809.80 : 13,538.10 = 5,561.20 : x
2. Step 2: Convert to fraction form
   9,809.80/13,538.10 = 5,561.20/x
3. Step 3: Cross multiply
   9,809.80x = 13,538.10 × 5,561.20
4. Step 4: Simplify right side
   9,809.80x = 75,288,081.72
5. Step 5: Solve for x
   x = 75,288,081.72/9,809.80
6. Step 6: Final answer
   x = 7,674.78