Finding the Fourth Proportional to 1,665.67, 2,498.49 and 639.67

Step by Step Solution

1. Step 1: Write the proportion equation
   1,665.67 : 2,498.49 = 639.67 : x
2. Step 2: Convert to fraction form
   1,665.67/2,498.49 = 639.67/x
3. Step 3: Cross multiply
   1,665.67x = 2,498.49 × 639.67
4. Step 4: Simplify right side
   1,665.67x = 1,598,209.10
5. Step 5: Solve for x
   x = 1,598,209.10/1,665.67
6. Step 6: Final answer
   x = 959.50