Finding the Fourth Proportional to 1,563.78, 2,345.51 and 639.42

Step by Step Solution

1. Step 1: Write the proportion equation
   1,563.78 : 2,345.51 = 639.42 : x
2. Step 2: Convert to fraction form
   1,563.78/2,345.51 = 639.42/x
3. Step 3: Cross multiply
   1,563.78x = 2,345.51 × 639.42
4. Step 4: Simplify right side
   1,563.78x = 1,499,766.00
5. Step 5: Solve for x
   x = 1,499,766.00/1,563.78
6. Step 6: Final answer
   x = 959.06