Finding the Fourth Proportional to 143.98, 215.76 and 139.58

Step by Step Solution

1. Step 1: Write the proportion equation
   143.98 : 215.76 = 139.58 : x
2. Step 2: Convert to fraction form
   143.98/215.76 = 139.58/x
3. Step 3: Cross multiply
   143.98x = 215.76 × 139.58
4. Step 4: Simplify right side
   143.98x = 30,115.78
5. Step 5: Solve for x
   x = 30,115.78/143.98
6. Step 6: Final answer
   x = 209.17