Finding the Fourth Proportional to 1,665.58, 2,498.69 and 639.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,665.58 : 2,498.69 = 639.50 : x
2. Step 2: Convert to fraction form
   1,665.58/2,498.69 = 639.50/x
3. Step 3: Cross multiply
   1,665.58x = 2,498.69 × 639.50
4. Step 4: Simplify right side
   1,665.58x = 1,597,912.26
5. Step 5: Solve for x
   x = 1,597,912.26/1,665.58
6. Step 6: Final answer
   x = 959.37