Finding the Fourth Proportional to 1,390.31, 2,085.89 and 805.18

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.31 : 2,085.89 = 805.18 : x
2. Step 2: Convert to fraction form
   1,390.31/2,085.89 = 805.18/x
3. Step 3: Cross multiply
   1,390.31x = 2,085.89 × 805.18
4. Step 4: Simplify right side
   1,390.31x = 1,679,507.67
5. Step 5: Solve for x
   x = 1,679,507.67/1,390.31
6. Step 6: Final answer
   x = 1,208.01