Finding the Fourth Proportional to 1,007.78, 1,390.76 and 565.67

Step by Step Solution

1. Step 1: Write the proportion equation
   1,007.78 : 1,390.76 = 565.67 : x
2. Step 2: Convert to fraction form
   1,007.78/1,390.76 = 565.67/x
3. Step 3: Cross multiply
   1,007.78x = 1,390.76 × 565.67
4. Step 4: Simplify right side
   1,007.78x = 786,711.86
5. Step 5: Solve for x
   x = 786,711.86/1,007.78
6. Step 6: Final answer
   x = 780.64