Finding the Fourth Proportional to 1,105.50, 1,525.59 and 639.75

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.50 : 1,525.59 = 639.75 : x
2. Step 2: Convert to fraction form
   1,105.50/1,525.59 = 639.75/x
3. Step 3: Cross multiply
   1,105.50x = 1,525.59 × 639.75
4. Step 4: Simplify right side
   1,105.50x = 975,996.20
5. Step 5: Solve for x
   x = 975,996.20/1,105.50
6. Step 6: Final answer
   x = 882.86