Finding the Fourth Proportional to 1,139.96, 1,710.17 and 399.65

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.96 : 1,710.17 = 399.65 : x
2. Step 2: Convert to fraction form
   1,139.96/1,710.17 = 399.65/x
3. Step 3: Cross multiply
   1,139.96x = 1,710.17 × 399.65
4. Step 4: Simplify right side
   1,139.96x = 683,458.89
5. Step 5: Solve for x
   x = 683,458.89/1,139.96
6. Step 6: Final answer
   x = 599.55