Finding the Fourth Proportional to 144.39, 215.43 and 139.98

Step by Step Solution

1. Step 1: Write the proportion equation
   144.39 : 215.43 = 139.98 : x
2. Step 2: Convert to fraction form
   144.39/215.43 = 139.98/x
3. Step 3: Cross multiply
   144.39x = 215.43 × 139.98
4. Step 4: Simplify right side
   144.39x = 30,155.89
5. Step 5: Solve for x
   x = 30,155.89/144.39
6. Step 6: Final answer
   x = 208.85