Finding the Fourth Proportional to 1,438.78, 1,985.72 and 809.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,438.78 : 1,985.72 = 809.56 : x
2. Step 2: Convert to fraction form
   1,438.78/1,985.72 = 809.56/x
3. Step 3: Cross multiply
   1,438.78x = 1,985.72 × 809.56
4. Step 4: Simplify right side
   1,438.78x = 1,607,550.47
5. Step 5: Solve for x
   x = 1,607,550.47/1,438.78
6. Step 6: Final answer
   x = 1,117.30