Finding the Fourth Proportional to 1,081.86, 1,492.94 and 639.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,081.86 : 1,492.94 = 639.78 : x
2. Step 2: Convert to fraction form
   1,081.86/1,492.94 = 639.78/x
3. Step 3: Cross multiply
   1,081.86x = 1,492.94 × 639.78
4. Step 4: Simplify right side
   1,081.86x = 955,149.95
5. Step 5: Solve for x
   x = 955,149.95/1,081.86
6. Step 6: Final answer
   x = 882.88