Finding the Fourth Proportional to 1,439.58, 1,986.54 and 810.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,439.58 : 1,986.54 = 810.21 : x
2. Step 2: Convert to fraction form
   1,439.58/1,986.54 = 810.21/x
3. Step 3: Cross multiply
   1,439.58x = 1,986.54 × 810.21
4. Step 4: Simplify right side
   1,439.58x = 1,609,514.57
5. Step 5: Solve for x
   x = 1,609,514.57/1,439.58
6. Step 6: Final answer
   x = 1,118.04