Finding the Fourth Proportional to 1,405.29, 1,939.32 and 815.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,405.29 : 1,939.32 = 815.79 : x
2. Step 2: Convert to fraction form
   1,405.29/1,939.32 = 815.79/x
3. Step 3: Cross multiply
   1,405.29x = 1,939.32 × 815.79
4. Step 4: Simplify right side
   1,405.29x = 1,582,077.86
5. Step 5: Solve for x
   x = 1,582,077.86/1,405.29
6. Step 6: Final answer
   x = 1,125.80