Finding the Fourth Proportional to 1,288.28, 1,777.86 and 764.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,288.28 : 1,777.86 = 764.72 : x
2. Step 2: Convert to fraction form
   1,288.28/1,777.86 = 764.72/x
3. Step 3: Cross multiply
   1,288.28x = 1,777.86 × 764.72
4. Step 4: Simplify right side
   1,288.28x = 1,359,565.10
5. Step 5: Solve for x
   x = 1,359,565.10/1,288.28
6. Step 6: Final answer
   x = 1,055.33