Finding the Fourth Proportional to 1,007.89, 1,390.94 and 565.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,007.89 : 1,390.94 = 565.78 : x
2. Step 2: Convert to fraction form
   1,007.89/1,390.94 = 565.78/x
3. Step 3: Cross multiply
   1,007.89x = 1,390.94 × 565.78
4. Step 4: Simplify right side
   1,007.89x = 786,966.03
5. Step 5: Solve for x
   x = 786,966.03/1,007.89
6. Step 6: Final answer
   x = 780.81