Finding the Fourth Proportional to 1,105.59, 1,525.55 and 639.75

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.59 : 1,525.55 = 639.75 : x
2. Step 2: Convert to fraction form
   1,105.59/1,525.55 = 639.75/x
3. Step 3: Cross multiply
   1,105.59x = 1,525.55 × 639.75
4. Step 4: Simplify right side
   1,105.59x = 975,967.41
5. Step 5: Solve for x
   x = 975,967.41/1,105.59
6. Step 6: Final answer
   x = 882.76