Finding the Fourth Proportional to 139.55, 209.15 and 71.10

Step by Step Solution

1. Step 1: Write the proportion equation
   139.55 : 209.15 = 71.10 : x
2. Step 2: Convert to fraction form
   139.55/209.15 = 71.10/x
3. Step 3: Cross multiply
   139.55x = 209.15 × 71.10
4. Step 4: Simplify right side
   139.55x = 14,869.52
5. Step 5: Solve for x
   x = 14,869.52/139.55
6. Step 6: Final answer
   x = 106.55