Finding the Fourth Proportional to 139.15, 191.91 and 83.89

Step by Step Solution

1. Step 1: Write the proportion equation
   139.15 : 191.91 = 83.89 : x
2. Step 2: Convert to fraction form
   139.15/191.91 = 83.89/x
3. Step 3: Cross multiply
   139.15x = 191.91 × 83.89
4. Step 4: Simplify right side
   139.15x = 16,099.33
5. Step 5: Solve for x
   x = 16,099.33/139.15
6. Step 6: Final answer
   x = 115.70