Finding the Fourth Proportional to 139.18, 208.72 and 58

Step by Step Solution

1. Step 1: Write the proportion equation
   139.18 : 208.72 = 58 : x
2. Step 2: Convert to fraction form
   139.18/208.72 = 58/x
3. Step 3: Cross multiply
   139.18x = 208.72 × 58
4. Step 4: Simplify right side
   139.18x = 12,105.91
5. Step 5: Solve for x
   x = 12,105.91/139.18
6. Step 6: Final answer
   x = 86.98