Finding the Fourth Proportional to 1,613.69, 2,420.69 and 639.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,613.69 : 2,420.69 = 639.56 : x
2. Step 2: Convert to fraction form
   1,613.69/2,420.69 = 639.56/x
3. Step 3: Cross multiply
   1,613.69x = 2,420.69 × 639.56
4. Step 4: Simplify right side
   1,613.69x = 1,548,179.35
5. Step 5: Solve for x
   x = 1,548,179.35/1,613.69
6. Step 6: Final answer
   x = 959.40