Finding the Fourth Proportional to 1,405.20, 1,939.24 and 775.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,405.20 : 1,939.24 = 775.76 : x
2. Step 2: Convert to fraction form
   1,405.20/1,939.24 = 775.76/x
3. Step 3: Cross multiply
   1,405.20x = 1,939.24 × 775.76
4. Step 4: Simplify right side
   1,405.20x = 1,504,384.82
5. Step 5: Solve for x
   x = 1,504,384.82/1,405.20
6. Step 6: Final answer
   x = 1,070.58