Finding the Fourth Proportional to 139.89, 209.94 and 71.40

Step by Step Solution

1. Step 1: Write the proportion equation
   139.89 : 209.94 = 71.40 : x
2. Step 2: Convert to fraction form
   139.89/209.94 = 71.40/x
3. Step 3: Cross multiply
   139.89x = 209.94 × 71.40
4. Step 4: Simplify right side
   139.89x = 14,989.72
5. Step 5: Solve for x
   x = 14,989.72/139.89
6. Step 6: Final answer
   x = 107.15