Finding the Fourth Proportional to 139.50, 209.01 and 85.29

Step by Step Solution

1. Step 1: Write the proportion equation
   139.50 : 209.01 = 85.29 : x
2. Step 2: Convert to fraction form
   139.50/209.01 = 85.29/x
3. Step 3: Cross multiply
   139.50x = 209.01 × 85.29
4. Step 4: Simplify right side
   139.50x = 17,826.46
5. Step 5: Solve for x
   x = 17,826.46/139.50
6. Step 6: Final answer
   x = 127.79