Finding the Fourth Proportional to 139.37, 208.76 and 100.80

Step by Step Solution

1. Step 1: Write the proportion equation
   139.37 : 208.76 = 100.80 : x
2. Step 2: Convert to fraction form
   139.37/208.76 = 100.80/x
3. Step 3: Cross multiply
   139.37x = 208.76 × 100.80
4. Step 4: Simplify right side
   139.37x = 21,042.50
5. Step 5: Solve for x
   x = 21,042.50/139.37
6. Step 6: Final answer
   x = 150.99