Finding the Fourth Proportional to 100.69, 139.01 and 80.98

Step by Step Solution

1. Step 1: Write the proportion equation
   100.69 : 139.01 = 80.98 : x
2. Step 2: Convert to fraction form
   100.69/139.01 = 80.98/x
3. Step 3: Cross multiply
   100.69x = 139.01 × 80.98
4. Step 4: Simplify right side
   100.69x = 11,257.03
5. Step 5: Solve for x
   x = 11,257.03/100.69
6. Step 6: Final answer
   x = 111.80