Finding the Fourth Proportional to 1,389.18, 1,918.17 and 858.84

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.18 : 1,918.17 = 858.84 : x
2. Step 2: Convert to fraction form
   1,389.18/1,918.17 = 858.84/x
3. Step 3: Cross multiply
   1,389.18x = 1,918.17 × 858.84
4. Step 4: Simplify right side
   1,389.18x = 1,647,401.12
5. Step 5: Solve for x
   x = 1,647,401.12/1,389.18
6. Step 6: Final answer
   x = 1,185.88