Finding the Fourth Proportional to 100.96, 139.01 and 86.18

Step by Step Solution

1. Step 1: Write the proportion equation
   100.96 : 139.01 = 86.18 : x
2. Step 2: Convert to fraction form
   100.96/139.01 = 86.18/x
3. Step 3: Cross multiply
   100.96x = 139.01 × 86.18
4. Step 4: Simplify right side
   100.96x = 11,979.88
5. Step 5: Solve for x
   x = 11,979.88/100.96
6. Step 6: Final answer
   x = 118.66