Finding the Fourth Proportional to 1,042.72, 1,439.76 and 810.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,042.72 : 1,439.76 = 810.40 : x
2. Step 2: Convert to fraction form
   1,042.72/1,439.76 = 810.40/x
3. Step 3: Cross multiply
   1,042.72x = 1,439.76 × 810.40
4. Step 4: Simplify right side
   1,042.72x = 1,166,781.50
5. Step 5: Solve for x
   x = 1,166,781.50/1,042.72
6. Step 6: Final answer
   x = 1,118.98