Finding the Fourth Proportional to 1,005.31, 1,508.82 and 639.01

Step by Step Solution

1. Step 1: Write the proportion equation
   1,005.31 : 1,508.82 = 639.01 : x
2. Step 2: Convert to fraction form
   1,005.31/1,508.82 = 639.01/x
3. Step 3: Cross multiply
   1,005.31x = 1,508.82 × 639.01
4. Step 4: Simplify right side
   1,005.31x = 964,151.07
5. Step 5: Solve for x
   x = 964,151.07/1,005.31
6. Step 6: Final answer
   x = 959.06