Finding the Fourth Proportional to 28,456.56, 42,685.62 and 7,680

Step by Step Solution

1. Step 1: Write the proportion equation
   28,456.56 : 42,685.62 = 7,680 : x
2. Step 2: Convert to fraction form
   28,456.56/42,685.62 = 7,680/x
3. Step 3: Cross multiply
   28,456.56x = 42,685.62 × 7,680
4. Step 4: Simplify right side
   28,456.56x = 327,825,561.60
5. Step 5: Solve for x
   x = 327,825,561.60/28,456.56
6. Step 6: Final answer
   x = 11,520.21