Finding the Fourth Proportional to 139.76, 208.78 and 100.91

Step by Step Solution

1. Step 1: Write the proportion equation
   139.76 : 208.78 = 100.91 : x
2. Step 2: Convert to fraction form
   139.76/208.78 = 100.91/x
3. Step 3: Cross multiply
   139.76x = 208.78 × 100.91
4. Step 4: Simplify right side
   139.76x = 21,067.99
5. Step 5: Solve for x
   x = 21,067.99/139.76
6. Step 6: Final answer
   x = 150.74