Finding the Fourth Proportional to 1,105.56, 1,525.58 and 639.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.56 : 1,525.58 = 639.72 : x
2. Step 2: Convert to fraction form
   1,105.56/1,525.58 = 639.72/x
3. Step 3: Cross multiply
   1,105.56x = 1,525.58 × 639.72
4. Step 4: Simplify right side
   1,105.56x = 975,944.04
5. Step 5: Solve for x
   x = 975,944.04/1,105.56
6. Step 6: Final answer
   x = 882.76