Finding the Fourth Proportional to 139.82, 209.86 and 71.39

Step by Step Solution

1. Step 1: Write the proportion equation
   139.82 : 209.86 = 71.39 : x
2. Step 2: Convert to fraction form
   139.82/209.86 = 71.39/x
3. Step 3: Cross multiply
   139.82x = 209.86 × 71.39
4. Step 4: Simplify right side
   139.82x = 14,981.91
5. Step 5: Solve for x
   x = 14,981.91/139.82
6. Step 6: Final answer
   x = 107.15