Finding the Fourth Proportional to 1,087.74, 1,500.98 and 639.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,087.74 : 1,500.98 = 639.57 : x
2. Step 2: Convert to fraction form
   1,087.74/1,500.98 = 639.57/x
3. Step 3: Cross multiply
   1,087.74x = 1,500.98 × 639.57
4. Step 4: Simplify right side
   1,087.74x = 959,978.58
5. Step 5: Solve for x
   x = 959,978.58/1,087.74
6. Step 6: Final answer
   x = 882.54