Finding the Fourth Proportional to 1,139.32, 1,707.95 and 408.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.32 : 1,707.95 = 408.72 : x
2. Step 2: Convert to fraction form
   1,139.32/1,707.95 = 408.72/x
3. Step 3: Cross multiply
   1,139.32x = 1,707.95 × 408.72
4. Step 4: Simplify right side
   1,139.32x = 698,072.30
5. Step 5: Solve for x
   x = 698,072.30/1,139.32
6. Step 6: Final answer
   x = 612.71