Finding the Fourth Proportional to 1,140, 1,581.60 and 1,129.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,140 : 1,581.60 = 1,129.20 : x
2. Step 2: Convert to fraction form
   1,140/1,581.60 = 1,129.20/x
3. Step 3: Cross multiply
   1,140x = 1,581.60 × 1,129.20
4. Step 4: Simplify right side
   1,140x = 1,785,942.72
5. Step 5: Solve for x
   x = 1,785,942.72/1,140
6. Step 6: Final answer
   x = 1,566.62