Finding the Fourth Proportional to 2,576.72, 3,865.56 and 821.60

Step by Step Solution

1. Step 1: Write the proportion equation
   2,576.72 : 3,865.56 = 821.60 : x
2. Step 2: Convert to fraction form
   2,576.72/3,865.56 = 821.60/x
3. Step 3: Cross multiply
   2,576.72x = 3,865.56 × 821.60
4. Step 4: Simplify right side
   2,576.72x = 3,175,944.10
5. Step 5: Solve for x
   x = 3,175,944.10/2,576.72
6. Step 6: Final answer
   x = 1,232.55