Finding the Fourth Proportional to 1,080.21, 1,490.50 and 638.09

Step by Step Solution

1. Step 1: Write the proportion equation
   1,080.21 : 1,490.50 = 638.09 : x
2. Step 2: Convert to fraction form
   1,080.21/1,490.50 = 638.09/x
3. Step 3: Cross multiply
   1,080.21x = 1,490.50 × 638.09
4. Step 4: Simplify right side
   1,080.21x = 951,073.15
5. Step 5: Solve for x
   x = 951,073.15/1,080.21
6. Step 6: Final answer
   x = 880.45