Finding the Fourth Proportional to 1,288.56, 1,778.18 and 764.58

Step by Step Solution

1. Step 1: Write the proportion equation
   1,288.56 : 1,778.18 = 764.58 : x
2. Step 2: Convert to fraction form
   1,288.56/1,778.18 = 764.58/x
3. Step 3: Cross multiply
   1,288.56x = 1,778.18 × 764.58
4. Step 4: Simplify right side
   1,288.56x = 1,359,560.86
5. Step 5: Solve for x
   x = 1,359,560.86/1,288.56
6. Step 6: Final answer
   x = 1,055.10