Finding the Fourth Proportional to 1,553.76, 2,142.72 and 1,087.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,553.76 : 2,142.72 = 1,087.20 : x
2. Step 2: Convert to fraction form
   1,553.76/2,142.72 = 1,087.20/x
3. Step 3: Cross multiply
   1,553.76x = 2,142.72 × 1,087.20
4. Step 4: Simplify right side
   1,553.76x = 2,329,565.18
5. Step 5: Solve for x
   x = 2,329,565.18/1,553.76
6. Step 6: Final answer
   x = 1,499.31