Finding the Fourth Proportional to 1,079.91, 1,490.31 and 638.10

Step by Step Solution

1. Step 1: Write the proportion equation
   1,079.91 : 1,490.31 = 638.10 : x
2. Step 2: Convert to fraction form
   1,079.91/1,490.31 = 638.10/x
3. Step 3: Cross multiply
   1,079.91x = 1,490.31 × 638.10
4. Step 4: Simplify right side
   1,079.91x = 950,966.81
5. Step 5: Solve for x
   x = 950,966.81/1,079.91
6. Step 6: Final answer
   x = 880.60