Finding the Fourth Proportional to 139.05, 208.58 and 57.89

Step by Step Solution

1. Step 1: Write the proportion equation
   139.05 : 208.58 = 57.89 : x
2. Step 2: Convert to fraction form
   139.05/208.58 = 57.89/x
3. Step 3: Cross multiply
   139.05x = 208.58 × 57.89
4. Step 4: Simplify right side
   139.05x = 12,074.93
5. Step 5: Solve for x
   x = 12,074.93/139.05
6. Step 6: Final answer
   x = 86.84