Finding the Fourth Proportional to 100.91, 139.01 and 80.18

Step by Step Solution

1. Step 1: Write the proportion equation
   100.91 : 139.01 = 80.18 : x
2. Step 2: Convert to fraction form
   100.91/139.01 = 80.18/x
3. Step 3: Cross multiply
   100.91x = 139.01 × 80.18
4. Step 4: Simplify right side
   100.91x = 11,144.73
5. Step 5: Solve for x
   x = 11,144.73/100.91
6. Step 6: Final answer
   x = 110.45