Finding the Fourth Proportional to 1,081.64, 1,492.56 and 639.68

Step by Step Solution

1. Step 1: Write the proportion equation
   1,081.64 : 1,492.56 = 639.68 : x
2. Step 2: Convert to fraction form
   1,081.64/1,492.56 = 639.68/x
3. Step 3: Cross multiply
   1,081.64x = 1,492.56 × 639.68
4. Step 4: Simplify right side
   1,081.64x = 954,760.78
5. Step 5: Solve for x
   x = 954,760.78/1,081.64
6. Step 6: Final answer
   x = 882.70