Finding the Fourth Proportional to 139.50, 209.28 and 43.31

Step by Step Solution

1. Step 1: Write the proportion equation
   139.50 : 209.28 = 43.31 : x
2. Step 2: Convert to fraction form
   139.50/209.28 = 43.31/x
3. Step 3: Cross multiply
   139.50x = 209.28 × 43.31
4. Step 4: Simplify right side
   139.50x = 9,064.60
5. Step 5: Solve for x
   x = 9,064.60/139.50
6. Step 6: Final answer
   x = 64.98