Finding the Fourth Proportional to 1,051.83, 1,575.69 and 639.95

Step by Step Solution

1. Step 1: Write the proportion equation
   1,051.83 : 1,575.69 = 639.95 : x
2. Step 2: Convert to fraction form
   1,051.83/1,575.69 = 639.95/x
3. Step 3: Cross multiply
   1,051.83x = 1,575.69 × 639.95
4. Step 4: Simplify right side
   1,051.83x = 1,008,352.54
5. Step 5: Solve for x
   x = 1,008,352.54/1,051.83
6. Step 6: Final answer
   x = 958.66