Finding the Fourth Proportional to 1,287.05, 1,929.58 and 638.24

Step by Step Solution

1. Step 1: Write the proportion equation
   1,287.05 : 1,929.58 = 638.24 : x
2. Step 2: Convert to fraction form
   1,287.05/1,929.58 = 638.24/x
3. Step 3: Cross multiply
   1,287.05x = 1,929.58 × 638.24
4. Step 4: Simplify right side
   1,287.05x = 1,231,523.90
5. Step 5: Solve for x
   x = 1,231,523.90/1,287.05
6. Step 6: Final answer
   x = 956.86