Finding the Fourth Proportional to 1,288.72, 1,778.16 and 764.92

Step by Step Solution

1. Step 1: Write the proportion equation
   1,288.72 : 1,778.16 = 764.92 : x
2. Step 2: Convert to fraction form
   1,288.72/1,778.16 = 764.92/x
3. Step 3: Cross multiply
   1,288.72x = 1,778.16 × 764.92
4. Step 4: Simplify right side
   1,288.72x = 1,360,150.15
5. Step 5: Solve for x
   x = 1,360,150.15/1,288.72
6. Step 6: Final answer
   x = 1,055.43