Finding the Fourth Proportional to 1,111.34, 1,533.70 and 639.39

Step by Step Solution

1. Step 1: Write the proportion equation
   1,111.34 : 1,533.70 = 639.39 : x
2. Step 2: Convert to fraction form
   1,111.34/1,533.70 = 639.39/x
3. Step 3: Cross multiply
   1,111.34x = 1,533.70 × 639.39
4. Step 4: Simplify right side
   1,111.34x = 980,632.44
5. Step 5: Solve for x
   x = 980,632.44/1,111.34
6. Step 6: Final answer
   x = 882.39