Finding the Fourth Proportional to 100.96, 139.28 and 71.89

Step by Step Solution

1. Step 1: Write the proportion equation
   100.96 : 139.28 = 71.89 : x
2. Step 2: Convert to fraction form
   100.96/139.28 = 71.89/x
3. Step 3: Cross multiply
   100.96x = 139.28 × 71.89
4. Step 4: Simplify right side
   100.96x = 10,012.84
5. Step 5: Solve for x
   x = 10,012.84/100.96
6. Step 6: Final answer
   x = 99.18