Finding the Fourth Proportional to 1,438.64, 1,985.15 and 809.10

Step by Step Solution

1. Step 1: Write the proportion equation
   1,438.64 : 1,985.15 = 809.10 : x
2. Step 2: Convert to fraction form
   1,438.64/1,985.15 = 809.10/x
3. Step 3: Cross multiply
   1,438.64x = 1,985.15 × 809.10
4. Step 4: Simplify right side
   1,438.64x = 1,606,170.89
5. Step 5: Solve for x
   x = 1,606,170.89/1,438.64
6. Step 6: Final answer
   x = 1,116.45