Finding the Fourth Proportional to 1,081.06, 1,491.31 and 638.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,081.06 : 1,491.31 = 638.20 : x
2. Step 2: Convert to fraction form
   1,081.06/1,491.31 = 638.20/x
3. Step 3: Cross multiply
   1,081.06x = 1,491.31 × 638.20
4. Step 4: Simplify right side
   1,081.06x = 951,748.32
5. Step 5: Solve for x
   x = 951,748.32/1,081.06
6. Step 6: Final answer
   x = 880.38