Finding the Fourth Proportional to 1,081.16, 1,492.30 and 639.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,081.16 : 1,492.30 = 639.31 : x
2. Step 2: Convert to fraction form
   1,081.16/1,492.30 = 639.31/x
3. Step 3: Cross multiply
   1,081.16x = 1,492.30 × 639.31
4. Step 4: Simplify right side
   1,081.16x = 954,034.85
5. Step 5: Solve for x
   x = 954,034.85/1,081.16
6. Step 6: Final answer
   x = 882.42