Finding the Fourth Proportional to 1,111.20, 1,665.36 and 726.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,111.20 : 1,665.36 = 726.72 : x
2. Step 2: Convert to fraction form
   1,111.20/1,665.36 = 726.72/x
3. Step 3: Cross multiply
   1,111.20x = 1,665.36 × 726.72
4. Step 4: Simplify right side
   1,111.20x = 1,210,250.42
5. Step 5: Solve for x
   x = 1,210,250.42/1,111.20
6. Step 6: Final answer
   x = 1,089.14