Finding the Fourth Proportional to 139.15, 208.56 and 100.42

Step by Step Solution

1. Step 1: Write the proportion equation
   139.15 : 208.56 = 100.42 : x
2. Step 2: Convert to fraction form
   139.15/208.56 = 100.42/x
3. Step 3: Cross multiply
   139.15x = 208.56 × 100.42
4. Step 4: Simplify right side
   139.15x = 20,944.06
5. Step 5: Solve for x
   x = 20,944.06/139.15
6. Step 6: Final answer
   x = 150.51