Finding the Fourth Proportional to 1,105.52, 1,525.60 and 639.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.52 : 1,525.60 = 639.76 : x
2. Step 2: Convert to fraction form
   1,105.52/1,525.60 = 639.76/x
3. Step 3: Cross multiply
   1,105.52x = 1,525.60 × 639.76
4. Step 4: Simplify right side
   1,105.52x = 976,017.86
5. Step 5: Solve for x
   x = 976,017.86/1,105.52
6. Step 6: Final answer
   x = 882.86