Finding the Fourth Proportional to 139.40, 208.68 and 98.72

Step by Step Solution

1. Step 1: Write the proportion equation
   139.40 : 208.68 = 98.72 : x
2. Step 2: Convert to fraction form
   139.40/208.68 = 98.72/x
3. Step 3: Cross multiply
   139.40x = 208.68 × 98.72
4. Step 4: Simplify right side
   139.40x = 20,600.89
5. Step 5: Solve for x
   x = 20,600.89/139.40
6. Step 6: Final answer
   x = 147.78