Finding the Fourth Proportional to 139.78, 209.55 and 48.47

Step by Step Solution

1. Step 1: Write the proportion equation
   139.78 : 209.55 = 48.47 : x
2. Step 2: Convert to fraction form
   139.78/209.55 = 48.47/x
3. Step 3: Cross multiply
   139.78x = 209.55 × 48.47
4. Step 4: Simplify right side
   139.78x = 10,156.89
5. Step 5: Solve for x
   x = 10,156.89/139.78
6. Step 6: Final answer
   x = 72.67