Finding the Fourth Proportional to 1,111.22, 1,533.48 and 639.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,111.22 : 1,533.48 = 639.21 : x
2. Step 2: Convert to fraction form
   1,111.22/1,533.48 = 639.21/x
3. Step 3: Cross multiply
   1,111.22x = 1,533.48 × 639.21
4. Step 4: Simplify right side
   1,111.22x = 980,210.00
5. Step 5: Solve for x
   x = 980,210.00/1,111.22
6. Step 6: Final answer
   x = 882.10