Finding the Fourth Proportional to 139.21, 208.71 and 100.69

Step by Step Solution

1. Step 1: Write the proportion equation
   139.21 : 208.71 = 100.69 : x
2. Step 2: Convert to fraction form
   139.21/208.71 = 100.69/x
3. Step 3: Cross multiply
   139.21x = 208.71 × 100.69
4. Step 4: Simplify right side
   139.21x = 21,015.01
5. Step 5: Solve for x
   x = 21,015.01/139.21
6. Step 6: Final answer
   x = 150.96