Finding the Fourth Proportional to 1,081.78, 1,492.77 and 639.59

Step by Step Solution

1. Step 1: Write the proportion equation
   1,081.78 : 1,492.77 = 639.59 : x
2. Step 2: Convert to fraction form
   1,081.78/1,492.77 = 639.59/x
3. Step 3: Cross multiply
   1,081.78x = 1,492.77 × 639.59
4. Step 4: Simplify right side
   1,081.78x = 954,764.50
5. Step 5: Solve for x
   x = 954,764.50/1,081.78
6. Step 6: Final answer
   x = 882.59