Finding the Fourth Proportional to 1,645.86, 2,470.04 and 780.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,645.86 : 2,470.04 = 780.78 : x
2. Step 2: Convert to fraction form
   1,645.86/2,470.04 = 780.78/x
3. Step 3: Cross multiply
   1,645.86x = 2,470.04 × 780.78
4. Step 4: Simplify right side
   1,645.86x = 1,928,557.83
5. Step 5: Solve for x
   x = 1,928,557.83/1,645.86
6. Step 6: Final answer
   x = 1,171.76