Finding the Fourth Proportional to 1,561.76, 2,155.32 and 863.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,561.76 : 2,155.32 = 863.20 : x
2. Step 2: Convert to fraction form
   1,561.76/2,155.32 = 863.20/x
3. Step 3: Cross multiply
   1,561.76x = 2,155.32 × 863.20
4. Step 4: Simplify right side
   1,561.76x = 1,860,472.22
5. Step 5: Solve for x
   x = 1,860,472.22/1,561.76
6. Step 6: Final answer
   x = 1,191.27