Finding the Fourth Proportional to 100.71, 139.10 and 89.09

Step by Step Solution

1. Step 1: Write the proportion equation
   100.71 : 139.10 = 89.09 : x
2. Step 2: Convert to fraction form
   100.71/139.10 = 89.09/x
3. Step 3: Cross multiply
   100.71x = 139.10 × 89.09
4. Step 4: Simplify right side
   100.71x = 12,392.42
5. Step 5: Solve for x
   x = 12,392.42/100.71
6. Step 6: Final answer
   x = 123.05