Finding the Fourth Proportional to 1,139.60, 1,707.78 and 728.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.60 : 1,707.78 = 728.12 : x
2. Step 2: Convert to fraction form
   1,139.60/1,707.78 = 728.12/x
3. Step 3: Cross multiply
   1,139.60x = 1,707.78 × 728.12
4. Step 4: Simplify right side
   1,139.60x = 1,243,468.77
5. Step 5: Solve for x
   x = 1,243,468.77/1,139.60
6. Step 6: Final answer
   x = 1,091.14