Finding the Fourth Proportional to 1,081.69, 1,492.04 and 639.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,081.69 : 1,492.04 = 639.28 : x
2. Step 2: Convert to fraction form
   1,081.69/1,492.04 = 639.28/x
3. Step 3: Cross multiply
   1,081.69x = 1,492.04 × 639.28
4. Step 4: Simplify right side
   1,081.69x = 953,822.81
5. Step 5: Solve for x
   x = 953,822.81/1,081.69
6. Step 6: Final answer
   x = 881.79