Finding the Fourth Proportional to 139.55, 208.71 and 85.48

Step by Step Solution

1. Step 1: Write the proportion equation
   139.55 : 208.71 = 85.48 : x
2. Step 2: Convert to fraction form
   139.55/208.71 = 85.48/x
3. Step 3: Cross multiply
   139.55x = 208.71 × 85.48
4. Step 4: Simplify right side
   139.55x = 17,840.01
5. Step 5: Solve for x
   x = 17,840.01/139.55
6. Step 6: Final answer
   x = 127.84